MIRROR  LAKE,  YOSEMITE. 


FIRST  YEAR  SCIENCE 


BY 


WILLIAM    H.    SNYDER,    Sc.D. 

PRINCIPAL   OF   THE   HOLLYWOOD    HIGH    SCHOOL 
LOS   ANGELES 


ALLYN   AND   BACON 

g0rfc  C 


COPYRIGHT,  1914,  BY 
WILLIAM   H.  SNYDER. 


DDO 


J.  8.  Gushing  Co.  —  Berwick  &  Smith  Co. 
Norwood,  Mass.,  U.S.A. 


PREFACE 

FIRST  YEAR  SCIENCE  deals  with  the  earth  and  the  sun  in 
their  relations  to  man.  This  treatment  has  three  advantages : 
it  gives  the  book  unity ;  it  gives  practical  interest ;  and  it  offers 
all  the  earth  science  needed  to  meet  such  requirements  as  those 
of  the  College  Entrance  Examination  Board. 

The  book  is  meant  for  immature  students.  For  this  reason  the 
language  is  simple,  not  technical,  and  the  principles  are  thor- 
oughly illustrated  by  experiments  and  pictures.  A  treatment 
too  terse  and  condensed  tends  to  confuse  young  students; 
hence  the  topics  in  First  Year  Science  are  sufficiently  discussed 
to  enable  young  pupils  to  master  them  with  ease. 

All  subjects  of  elementary  school  science — physics,  chemis- 
try, meteorology,  botany,  zoology,  physiology,  astronomy, 
physiography,  forestry,  and  agriculture  —  are  treated,  so  that 
the  pupil  can  find  out  for  himself  which  ones  he  wishes  to  study 
later  in  the  course. 

The  book  is  complete  in  itself;  no  reference  library,  no 
manual,  is  needed.  The  experiments  require  only  the  simplest 
apparatus.  In  most  cases  the  mere  reading  of  them  is  sufficient 
to  illustrate  the  text. 

The  separate  chapters,  while  forming  links  in  the  develop- 
ment of  the  whole  subject,  are  in  most  cases  separate  units, 
any  one  of  which  may  be  omitted  when  time  for  it  is  lacking. 
Each  chapter  closes  with  a  pithy  summary  and  suggestive 
questions. 

The  book  deals  with  the  large  and  concrete  things  which 
surround  boys  and  girls  and  in  which  they  are  naturally  in- 
terested. There  is  little  abstract  theory,  the  effort  being  to 
call  attention  to  things  that  can  be  seen  and  appreciated. 

iii 

296611 


IV  PREFACE 

.•j 

Practical   things,   and   facts   which  their  other  studies  have 
made  familiar,  are  always  used  for  illustration. 

First  Year  Science  is  the  outgrowth  of  the  effort  of  a  com- 
mittee of  the  Los  Angeles  teachers  to  make  a  simple,  unified 
course  in  General  Science  for  the  upper  grades  of  the  interme- 
diate schools  and  the  first  year  of  the  high  schools.  It  has 
been  carefully  tested  in  the  Los  Angeles  schools. 

To  the  other  members  of  this  committee,  Principal  J.  B. 
Lillard  of  the  Gardena  Agricultural  High  School  and  Princi- 
pal Ealph  C.  Daniels  of  the  San  Pedro  High  School,  and  also 
to  all  the  teachers  of  first  year  science  in  the  intermediate  and 
high  schools  of  Los  Angeles  who  carefully  tried  out  the  book 
in  their  classes,  the  author  extends  grateful  acknowledgment. 
The  proof  was  carefully  read  by  J.  M.  Sniffen  and  Claude  W. 
Sandifur,  but  the  author  wishes  to  absolve  them  from  respon- 
sibility for  any  errors  that  may  have  crept  in.  Their  assistance 
and  suggestions  were  of  the  greatest  service. 

W.  H.  S. 

OCTOBER,  1914. 


ACKNOWLEDGMENT  OF  ILLUSTRATIONS 

For  all  line  drawings,  H.  W.  Miles  and  Miss  Yvonne  Rob- 
inson, High  School,  Hollywood,  Cal. 

Paul  V.  Bacon,  Boston,  Mass.,  11,  133,  157,  318,  432. 
Brown  and  Dawson,  Stamford,  Conn.,  287. 

E.  C.  Chamberlin,  San  Francisco,  247. 

W.  A.  Dunn,  Principal  Polytechnic  High  School,  Los  Angeles, 
76,  79. 

Professor  W.  A.  Fisk,  Ontario,  Cal.,  80,  189,  256,  267,  273, 
298,  302,  347,  349,  364,  367,  369,  374,  385,  420,  452. 

Joseph  Giroux,  Hollywood  High  School,  Cal.,  78. 

Graham  Photo  Co.,  Los  Angeles,  254,  259. 

F.  M.  Hallet,  Los  Angeles,  177,  251,  255,  268,  269,  406. 
L.  L.  Hill,  Los  Angeles,  245. 


ACKNOWLEDGMENT   OF  ILLUSTRATIONS  v 

Howell,  Washington,  D.  C.,  288  and  289. 

Los  Angeles  Times,  246. 

Professor  McAdie,  Blue  Hill  Observatory,  Milton,  Mass., 
126,  127,  164. 

Mt.  Wilson  Solar  Observatory,  Mt.  Wilson,  Cal.,  1,  2,  3,  4, 12. 

C.  C.  Pierce  &  Co.,  Los  Angeles,  63,  69,  70,  71,  82,  95,  96,  99, 
101,  102,  103,  105,  106,  182,  191,  199,  200,  201,  202,  204,  206, 
210,  221,  223,  236,  237,  238,  248,  250,  252,  257,  258,  261,  315, 
316,  330,  345,  348,  395,  397,  398,  403,  404,  412,  414,  421,  427, 
434,  450,  451. 

Putnam  and  Valentine,  Los  Angeles,  146,  176,  243,  245,  278, 
333,  366,  371,  410,  413,  440,  442. 

Salt  Lake  Ry.,  323. 

San  Francisco  Board  of  Trade,  308,  309. 

Miss  Alice  M.  Sinclair,  Manual  Arts  High  School,  Los 
Angeles,  169,  170. 

Southern  Pacific  Ey.,  335. 

Chas.  S.  Thompson,  San  Pedro  High  School,  Los  Angeles, 
186,  252,  260. 

H.  C.  Tracy,  Hollywood  High  School,  Cal.,  433. 

Underwood  and  Underwood,  New  York  City,  86,  445. 

C.  J.  Van  Vliet,  Los  Angeles,  59. 

U.  S.  Bureau  of  Agriculture,  218,  219,  405. 

U.  S.  Bureau  of  Forestry,  262,  263,  264,  265,  266,  326. 

U.  S.  Bureau  of  Soils,  93,  94,  95,  104, 159,  175, 198,  317,  387. 

U.  S.  Weather  Bureau,  171,  172,  173. 

U.  S.  Geological  Survey,  76,  77,  81,  84,  85,  92,  98,  100,  104, 
163,  313,  325,  327,  328,  334,  337,  338,  339,  340,  356,  357,  370, 
373,  375,  376,  380,  391,  401,  402,  415,  425,  426,  436,  449,  450. 

Allen  Watson,  Washington,  D.  C.,  13,  285. 

Eev.  C.  D.  Williams,  Los  Angeles,  Frontispiece. 


TABLE  OF  CONTENTS 


I.  THE  EARTH  AND  ITS  NEIGHBORS 1 

II.  THE  PLANET  EARTH 18 

III.  THE  GIFTS  OF  THE  SUN  x6  THE  EARTH      ...      45 

IV.  THE  EARTH'S  CRUST 68 

V.  THE  ATMOSPHERE  OF  THE  EARTH         ....     110 

VI.  THE  LIVE  PART  OF  THE  EARTH    .        .         .        .        .182 
VII.  LIFE  OF  THE  EARTH  AS  RELATED  TO  PHYSICAL  CON- 
DITIONS       242 

VIII.  THE  SEA .271 

IX.  COAST  LINES 292 

X.  WATER  SCULPTURE 313 

XL  ICE  AND  WIND  SCULPTURES 363 

XII.  Low  AREAS  OF  THE  EARTH 391 

XIII.  THE  HIGH  AREAS  OF  THE  EARTH        ....    409 

XIV.  VOLCANOES .        .440 

XV.  APPENDIX 455 


vii 


MAPS 

PAGE 

Map  showing  International  Date  Line 30 

Map  showing  Standard  Time  Belts    .         .         .         .         .  .31 

Lines  of  Equal  Magnetic  Declination  in  the  United  States  .  .  35 
Region  around  the  Magnetic  Pole  .......  36 

Heat  Belts 135 

Isothermal  Lines  for  January     .         .         .         .         .         .  136 

Isothermal  Lines  for  July 137 

Isobaric  Lines  for  January .         .         .140 

Isobaric  Lines  for  July       .         .         .         .         .         .         .         .         .141 

Wind  Map  for  July  and  August          .         .         .         .         .         .         .150 

Wind  Map  for  January  and  February 151 

Rainfall  Map  of  the  World 155 

Average  Rainfall  of  the  United  States       .         .         .        ..         .         .158 

Cyclones  and  Anticyclones 1 72 

Mean  Storm  Tracks  and  Average  Daily  Movements          .         .         .     1 73 

Ocean  Currents  of  the  World 280 

Nahant,  Massachusetts 297 

The  Platte  River 335 

The  Mississippi  and  Some  of  its  Abandoned  Meanders  .  .  .  338 
Incised  Meanders  (Government  Contour  Map),  colored  .  facing  345 
Mouths  of  the  Mississippi  .........  352 

Drainage  Basins  of  the  United  States 354 

Area  Covered  by  the  Ice  of  the  Glacial  Period 383 

The  Coast  near  Atlantic  City 394 

A  Submerged  Coastal  Plain 399 

Appalachian  Plateau          .         .         .         .         .         .        ...         .416 


ix 


ILLUSTRATIONS 

PAGE 

Part  of  the  Milky  Way 1 

Dome  of  the  60-inch  Reflecting  Telescope  at  Mount  Wilson  Solar 

Observatory        ..........  2 

Mars      .         .             4 

Three  Views  of  Saturn       .  ' 4 

Halley's  Comet          . 5 

Diagram  of  the  Solar  System     ........  6 

A  Biplane          : 9 

Three  Forces  in  Play 11 

Surface  of  the  Moon  .         .         .         .     • 12 

High  Tide  in  Nova  Scotia 13 

Low  Tide  at  the  Same  Place 13 

The  Phases  of  the  Moon 14 

Mount  Everest  ...........  17 

The  Himalaya  Mountains 19 

A  Cottage  in  the  Scotch  Highlands 20 

Medieval  Idea  of  the  Universe 22 

A  Laplander's  Hut 25 

The  Path  of  the  Earth  around  the  Sun 26 

A  Hut  in  the  Tropics 27 

Magnetic  Crane 38 

Transformation  of  Energy          ........  46 

Thermograph     .         . .51 

Hot  Water  Furnace 55 

A  Lake  Mirror •     .         .         .         .59 

A  Reflection  Engine 63 

Old  Sea  Beaches,  San  Pedro 69 

Old  Rock  Beach,  Imperial  Valley,  California 70 

Salt  Works  on  the  Shore  of  the  Salton  Sea 71 

Corals 74 

Granite      ....:....'...  76 

Fossil-bearing  Limestone 76 

Conglomerate    ...........  77 

Oil  Wells 78 

Gneiss                                                                                               .        ..  79 


ILL  US  TEA  TIONS  XI 

PAGE 

Stratified  Rock 80 

Folded  Rocks 81 

Rocks  weathering  and  forming  Deep  Slopes      .         .         .         .         .       82 

Cleopatra's  Needle,  Central  Park,  New  York 83 

Rocks  split  by  Roots  of  a  Tree  .......       84 

Wind-cut  Rocks .84 

Local  Soil 85 

Digging  Peat  in  Ireland     .         .         ...         .         .         .         .         .86 

Molehills 90 

Anthill 91 

Mud  Cracks 92 

Lumpy  Soil        .         .         .         .         . 93 

Adobe  Soil .         .         .94 

The  Cracking  of  Adobe  Soil  when  Dr^ 95 

Prairie  Scene 95 

Alfalfa  Root 96 

A  Natural  Spring 98 

An  Artesian  Spring 99 

"  Dry  Farming"  in  Egypt '.         .100 

Kaffir  Corn 101 

Irrigation  in  Squares          .         .         .         .         .         .         .         .         .102 

Irrigation  in  Furrows          .         .         .         .         .         .         .         .         .103 

Alkali  Soil 104 

Reclaiming  Alkali  Soil  in  the  Sahara 104 

Roman  Plowing         .         .         . 105 

Steam  Plow .     105 

Good  Soil 106 

Blue  Hill  Observatory,  Milton,  Mass .110 

Balloon 115 

Hot  Air  Furnace        .         . 117 

Barograph 121 

Cumulus  Clouds 126 

Fog 127 

Lick  Observatory 128 

A  Winter  Scene  in  Venice 133 

A  Winter  Scene  in  Montreal      .         .         .         .         .         .         .         .134 

A  Dutch  Windmill 145 

Effect  of  Wind  on  the  Growth  of  Trees 146 

A  Sailing  Vessel 147 

Wind  Belts  of  the  Earth 149 

Salmon  River  Dam,  Idaho 157 

East  End  of  the  Assuan  Dam  across  the  Nile     ,  159 


Xll  ILLUSTRATIONS 

PAGE 

A  Flash  of  Lightning          .         . 1 62 

Tree  completely  shattered  by  a  Stroke  of  Lightning  .         .         .163 

Thunder-storm  Clouds        .         .         .         .         .         .         .         .  1 64 

Wireless  Telegraph  Station,  Los  Angeles  .         .         .         .         .         .167 

A  Tornado 168 

The  Effects  of  a  Tornado 1 69 

Remains  of  Farm  Buildings  destroyed  by  a  Tornado          .         .  1 70 

Waterspout  Seen  off  the  Coast  of. New  England          .         .         .         .171 

A  Southern  Cotton  Field 175 

Yucca  Palm      .         . 176 

Camel 177 

A  Laplander 178 

A  South  Sea  Islander         .         .         .         . 1 79 

The  Rocky  Mountain  Giant       .         ^ 182 

A  Typical  Plant 183 

A  Pine  Tree 189 

An  Ivy  Branch 190 

A  Banyan  Tree 191 

Different  Forms  which  Leaves  Assume      .         .         .         .         .         .193 

A  Forest  of  Pines 198 

A  Sunflower  Plant 199 

Eucalyptus  Leaves     .         .         .         .         .         .         .         .     f    .         .     200 

Flower,  showing  Corolla,  Stamen,  and  Pistil     .         .         .         .         .201 

Pink  Gentian 201 

Mint  Flower 202 

Yucca,  or  Spanish  Bayonet        .         .  *      .  - 204 

Scrub  Oak  Branch 206 

Mistletoe  Growing  on  an  Oak     .         .         .         .         .         .         .         .210 

Preparing  Smoked  Fish  at  Gloucester 214 

Disease-bearing  Mosquito 218 

A  "  Malarial"  Swamp 219 

Earthworm 220 

Butterflies  on  Alfalfa 221 

Beehives . 223 

A  Human  Skeleton 224 

The  Nervous  System  of  Man 225 

The  Lungs          ...........     226 

The  Circulatory  System 229 

Cross  Section  of  the  Human  Heart 230 

Cross  Section  of  the  Human  Eye 231 

Cross  Section  of  the  Human  Ear        .         .         .         .         .         .         .231 

A  Date  Palm  236 


ILLUSTRATIONS  xiii 

PAGE 

A  Bunch  of  Dates 237 

Coffee  Plant 238 

Petrified  Trees 242 

Gila  Monsters 243 

Canada  Thistle 244 

A  Rattlesnake  coiled  ready  to  spring          ......  245 

Cacti 245 

A  Herd  of  Reindeer 245 

Tiger 246 

A  California  Rabbit  Drive 247 

Different  Kinds  of  Seaweed 248 

A  Small  Shark 249 

Flying  Fish 250 

Seal 251 

Prickly  Phlox 252 

Bird's  Nest 252 

A  Beaver  Dam 253 

Ostriches 254 

Opossum    ..............  255 

A  Kangaroo  Feeding 255 

Timber  Line  on  a  High  Mountain      .                  .         .         .         .         .  256 

Mesquit  Beans 257 

An  Oasis  in  the  Mojave  Desert 257 

A  Water  Hole  in  the  Desert 258 

A  Desert  and  Oasis .  259 

The  Dodo  .      '  .         .         .         .   ' 260 

Original  Flora  supplanted  by  New  Plants  .         .         .         .         .261 

Bad  Forestry 262 

Bad  Forestry 263 

Bad  Forestry 264 

Good  Forestry 265 

Good  Forestry            . 266 

A  California  Big  Tree 267 

Coyote 268 

Prairie  Dog 269 

The  Ocean 271 

Continental  Shelf 273 

Crinoid 276 

Globigerina 277 

Ocean  Waves 278 

Coral  Formations  in  the  Bermudas    . 283 

High  Tide  in  the  Bay  of  Fundy .  285 


XIV  ILL  US  TEA  TIONS 

f*  PAGE 

Low  Tide  at  the  Same  Place      .        .         .        .         .        .         .         .  285 

An  Atoll  in  the  Mid-Pacific 286 

The  Vaterland 287 

Panama  Canal  .         .      • *.-        .     288-289 

Positano 292 

North  Cape 293 

Fingal's  Cave 294 

An  Elevated  Rock  Bench 295 

A  Lake  Beach  formed  by  Stream  and  Wave  Action           .         .         .  296 

A  Sand  Spit 298 

A  Beach  at  Catalina  Island 299 

Inland  Sea  Cave  and  Beach 300 

Temple  ot  Jupiter  near  Naples  .         .        .  .         .         .         .301 

Sand  Dunes  formed  upon  a  Sand  Bar         .        .         .         .        .         .  302 

Part  of  the  Coast  of  Maine 304 

A  Norway  Fiord 305 

A  Norway  Fiord 306 

Norway  Village 306 

San  Francisco  Harbor .     308-309 

Minot's  Ledge  Lighthouse 310 

A  Hot  Spring  in  the  Yellowstone 313 

Flowing  Artesian  Well 315 

A  Limestone  Cave      . 316 

Montezuma's  Well 316 

Sink-hole  in  Tennessee  Limestone 317 

Great  Natural  Bridge,  Utah        .        .      "  .         .         .         .   '     .        .317 

Natural  Bridge,  Saxony 318 

Giant  Geyser  in  Eruption   .........  320 

Cone  of  the  Beehive  Geyser 321 

An  Undrained  Upland •  322 

Sunset  on  Great  Salt  Lake .  323 

The  Dead  Sea 324 

Lake  Drummond 325 

Gullies  being  cut  by  Running  Water 326 

The  Bad  Lands  of  Dakota 327 

Divides  between  Streams 328 

Yosemite  Fall 330 

Niagara  Falls 332 

Yellowstone  River 333 

A  Stream  working  back  into  an  Undissected  Area      ....  334 

River  Erosion 335 

River  Plain  336 


ILL  USTRA  TIONS  XV 

PAGE 

River  Meandering  in  its  Flood  Plain 337 

Levee  of  the  Lower  Mississippi  ........  338 

Levee  along  the  Sacramento 339 

An  Old  River 340 

Results  of  a  Sudden  Flood 341 

River  Terraces 344 

Intrenched  Meanders          .         .         .         .         .         .                  .  345 

Alluvial  Cones 347 

Fan-filled  Valley 348 

Lake  Delta 349 

Cone-shaped  Delta  in  Lake  Geneva    .        .         .        .         .         .         .  35Q 

Lake  Brienz  from  above  Interlaken 351 

The  "  Soo  "  Canal  at  Sault  Ste.  Marie 355 

The  Jetties  of  the  Mississippi           ,  .         .         .         .         .         .         .  356 

Delta  Land  of  the  Lower  Mississippi 356 

The  Columbia  River  and  its  Old  Flood  Plain 357 

The  Colorado  River 359 

Snow  Crystals 363 

Snow  Field  at  the  Head  of  a  Glacier 364 

The  Corner  Glacier 365 

Crevasses  in  a  Glacier 365 

The  Coe  Glacier,  Mount  Hood 366 

The  Dana  Glacier  in  the  High  Sierras 367 

The  Fiesch  Glacier 368 

A  Terminal  Moraine 369 

A  Bowlder  borne  along  on  Top  of  a  Glacier        .         .        .         .         .  369 

A  Stone  scratched  by  a  Glacier 370 

Rocks  polished  by  a  Glacier 370 

Mount  Hood       .         . .371 

A  View  of  the  Jungfrau 372 

An  Iceberg 373 

Bowlders  and  Sand  left  by  a  Retreating  Glacier          ....  374 

A  Drumlin 375 

An  Esker 376 

Glacial  Rock  Lake 377 

A  V-shaped  Valley  in  Norway 378 

A  Hanging  Valley 379 

A  Huge  Perched  Bowlder 380 

Marjelen  Lake 381 

Niagara  Falls .  382 

Electric  Plant  at  Niagara 385 

Tree  being  dug  up  by  the  Wind 387 


XVI  ILLUSTRA  TIONS 

PAGE 

A  Forest  on  Cape  Cod         .        .     f* 388 

Quarrying  a  Sand  Dune  to  make  Brick 389 

A  Level,  Poorly-drained  Area 39 1 

Rice  Swamp  at  the  Border  of  a  Narrow  Coastal  Plain,        •         •         .  395 

Crude  Turpentine  Still 396 

Cotton 397 

Pineapples 398 

Lake  Plain 401 

"Bottom  Lands" 402 

Alfalfa  Cutting  on  the  Fertile  Prairies 403 

A  High,  Dry  Plain      .                  404 

A  Herd  of  Cattle  on  the  Great  Plains 405 

Herd  of  Bison 406 

Part  of  the  Plain  of  Waterloo,  Belgium, 407 

Colorado  Plateau        .         .         .         .        .         .        .         .         .        .410 

The  Enchanted  Mesa 412 

A  Butte 412 

An  Indian  Hogan 413 

Cliff  Dwellings 414 

A  Fault 415 

Folded  Strata 420 

Massive  Mountains     .         .         .         .         .         .         .         .        ...  421 

Ben  Nevis 423 

The  Matterhorn 424 

The  Teton  Range 425 

Fault  Line  of  an  Earthquake 426 

Fence  Broken  by  Slipping  of  the  Earth  along  a  Fault  Line          .         .  426 

The  Result  of  an  Earthquake 427 

Placer  Mining  in  the  Sierras 427 

Deep  Down  in  the  Calumet  and  Hecla  Mine 428 

Top  of  Pike's  Peak 429 

Popocatepetl       ...........  430 

Landslide  in  Norway 431 

Landslide  at  Amalfi 432 

Rocky  Mountain  Goats       .........  433 

A  Mountain  Shepherd  with  his  Flocks         ....         .  434 

A  Near  View  of  the  Jungfrau     ........  435 

Cripple  Creek 436 

Mount  Shasta 440 

Cinder  Cone  near  Mount  Lassen         .......  442 

Vesuvius  and  Naples 443 

Mount  Vesuvius          .......  444 


ILLUSTRATIONS  xvii 

PAGE 

Mount  Pelee  and  the  Ruins  of  St.  Pierre 445 

San  Miguel  Harbor  in  the  Azores 447 

Mount  Lassen  in  Eruption 448 

Mount  Hood 449 

Volcanic  Necks  near  Mount  Taylor    ...         ....  449 

Crater  Lake 450 

Lava  Flow  in  the  Hawaiian  Islands     .......  450 

A  Hawaiian  Crater      .         .         ,         .         .         .         .         .         .         .451 

Cross  Section  of  a  Lava  Flow 452 

The  City  of  St.  Helena 453 


FIRST   YEAR   SCIENCE 


CHAPTER   I 
THE  EARTH  AND  ITS  NEIGHBORS 

1,  The  Evening  Sky.  —  As  the  light  of  the  sun  fades  in 
the  evening,  we  see  the  stars  coming  out  one  by  one  until 


PART  OF  THE  MILKY  WAY. 
The  plate  for  this  photograph  was  exposed  ten  hours  and  a  quarter. 

at  last  the  sky  is  studded  with  them.    We  notice,  too,  that 
the  brighter  the  star  is,   the  sooner   it  appears.     In  the 

1 


FIRST    YEAR   SCIENCE 


morning,  just  the  reverse  'of  this  takes  place,  the  stars 
begin  gradually  to  fade,  and  the  brightest  stars  are  the 
last  to  disappear. 

We  know  how  brilliant  the  light  of  a  match  or  candle 
appears  in  a  dark  room,  and  how  a  light  of  this  kind 


DOME  OF  THE  60-iNCH  REFLECTING  TELESCOPE  AT  MT.  WILSON  SOLAR 

OBSERVATORY. 
Pictures  of  the  heavens  are  taken  through  a  telescope. 

seems  to  fade  out  when  it  is  brought  into  the  pres- 
ence of  a  strong  electric  light.  It  would  seem  quite 
probable  that  the  vast  light  of  the  sun  might  have  the 
same  effect  upon  the  light  of  the  stars.  This  supposition 
is  also  supported  by  the  fact  that  when  the  sun  is  covered 


THE  EARTH  AS  A   PLANET  3 

in  an  eclipse  the  stars  begin  to  appear  as  in  the  evening. 
Astronomers  are  all  agreed  that  if  it  were  not  for  the 
greater  brilliancy  of  the  sun  we  should  see  the  heavens 
full  of  stars  all  the  time. 

In  the  northern  hemisphere  the  stars,  except  those  at 
the  north,  which  seem  to  go  around  in  a  circle,  appear  to 
rise  in  the  east  and  to  set  in  the  west,  just  as  the  sun  does. 
If  we  observe  the  stars  which  rise  to  the  east,  southeast, 
and  northeast  of  us,  we  shall  find  that  these  are  above  the 
horizon  for  different  lengths  of  time. 

The  ancients  noticed  these  facts,  and  explained  them 
by  saying  that  the  earth  was  at  the  center  of  a  hollow 
sphere,  upon  the  inner  surface  of  which  were  the  stars; 
and  that  this  sphere  was  continually  revolving  about  the 
earth  and  also  slightly  changing  its  position  in  respect  to 
the  earth.  We  of  the  present  day  know  that  it  is  the 
earth  that  is  turning  around  on  an  imaginary  axis,  and 
also  gradually  changing  its  position  in  relation  to  the 
stars.  We  also  know  that  this  axis,  if  extended  far 
enough,  would  almost  strike  &  star  in  the  center  of  the 
northern  heavens,  which  we  call  the  North  Star.  The 
points  on  the  surface  of  the  earth  through  which  the 
axis  passes  are  called  the  poles. 

2,  The  Earth  as  one  of  the  Planets.  —  If  we  carefully  ob- 
serve the  bright  points  which  appear  in  the  sky  at  night, 
we  shall  see  that  almost  all  of  them  shine  with  a  twinkling*' 
light.  There  are,  however,  three  of  the  brightest  which 
give  a  steady  light  like  that  of  the  moon.  When  the  po- 
sitions of  these  three  bodies  are  carefully  observed  for 
some  time,  it  will  be  seen  that  they  are  continually  chang- 
ing their  places  among  the  stars,  whereas  the  positions  of 
the  stars  do  not  appear  to  change  relatively  to  one  another. 

One  of  these  three  brightest  points  has  a  reddish  brown 
color  and  has  been  named  Mars,  from  the  Roman  god  of 


FIRST   YEAR   SCIENCE 


war.      The  other  two  bear  the  names  Venus  and  Jupiter, 
one  named  from  the  goddess  of  beauty  and  the  other  from 

the  king  of  the  Roman 
gods.  Astronomers  call 
the  earth  and  these  three 
bodies,  together  with 
four  others,  planets,  and 
tell  us  that  they  revolve 
around  the  sun  as  a 
center.  They  have  no 
light  of  their  own  as  do 
the  true  stars,  but  the 
light  which  comes  to  us 
from  them  is  a  reflection 
of  the  light  of  the  sun. 

The    unaided    eye   is 
able   at   some    times  to 


it 


MARS. 

Most  like  the  earth  of  all  the  planets, 
is  supposed  to  have  a  polar  ice  cap. 

see  five  of  these  planets. 

Astronomers  tell  us  that  their  change  of  place  in  rela- 
tion to  the  stars  is  due  to  their  motion  about  the  sun. 
If  we  could  stand  upon  one  of  these  visible  planets,  our 


THREE  VIEWS  OF  SATURN. 
The  planet  with  the  beautiful  rings. 


earth  would  appear  to  us  like  one  of  them.  But  the 
surface  of  some  of  these  planets,  like  Jupiter  or  Saturn, 
is  not  solid  like  that  of  the  earth.  Our  sun,  if  seen 


THE  EARTH  AS  A   PLANET  5 

from  the  distance  of  one  of  the  stars,  would  appear  like 
a  star. 

The  list  of  the  planets  in  the  order  of  distance  from  the 
sun  is :  Mercury,  Venus,  Earth,  Mars,  Jupiter,  Saturn, 
Uranus,  and  Neptune.  The  suu,  with  the  bodies  revolv- 
ing about  it,  is  called  the  solar  system.  There  is  reason  to 
believe  that  ours  is  only  one  of  many  similar  solar  systems 
that  exist  throughout  space. 


HALLEY'S  COMET. 

One  of  the  most  famous  visitors  from  outer  space.    The  small  white  dots 
are  stars  seen  through  the  tail. 

The  planets  are  by  far  the  nearest  of  all  the  starlike 
bodies,  although  the  distance  from  the  sun  to  the  farthest 
of  the  planets  is  some  2700  million  miles  greater  than  the 
distance  from   the   earth    to    the  sun.     The  distance    of 
the    nearest    of   the    stars    however,    is    probably    about 
25,000,000,000,000  miles.     This  distance  is  so  great  that! 
it  takes  light,  which  travels  at  the  inconceivable  rate  of  | 
186,000  miles  in  a  second  of  time,  over  four  and  a  half 
years   to   come   to    us   from  this   star.     From  Arcturus, 


6 


FIRST   YEAR   SCIENCE 


another  of  the  stars,  it  takes  light  about  180  years  to 
reach  us,  and  from  others  very  much  longer.  Sometimes 
from  this  outer  space  comets  visit  our  solar  system.  Thus 
we  see  that  our  little  earth  is  only  a  speck  in  the  universe. 
In  the  space  between  the  planets  Mars  and  Jupiter, 
there  has  been  found  a  group  of  small  bodies  which  are 
called  planetoids  or  asteroids.  The  brighest  of  these  is 
Vesta,  not  more  than  250  miles  in  diameter. 

A  famous  theory,  called  the  Nebular  Hypothesis,  was 
suggested  many  years  ago  to  account  for  the  formation  of 

our  solar  system.  This 
theory  supposes  that  the 
materials  of  which  the 
members  of  the  solar 
system  are  composed 
once  formed  a  cloud  or 
nebula  of  finely  divided 
matter  filling  an  enor- 
mous space,  and  that 
this  matter,  by  reason 
of  the  mutual  attrac- 
tion of  the  particles, 
gathered  together  into 
what  is  now  our  sun 
with  its  planets  and 

their  satellites.  No  one  knows  in  what  way  this  matter 
originated  or  how  matter  can  either  be  created  or  destroyed. 
But  we  do  know  many  of  the  properties  of  matter. 

3,  Properties  of  the  Matter  Composing  the  Universe.  — Experi- 
ment 1.  —  Pull  out  the  handle  of  a  compression  air-pump  or  bicycle 
pump.  Close  the  exit  valve  or  stop  up  the  end  of  the  bicycle  pump. 
Now  try  to  push  in  the  handle.  What  keeps  it  from  moving  easily? 
Try  to  shove  an  inverted  drinking  glass  into  a  pail  of  water.  Why 
does  not  the  water  fill  the  glass  ? 


DIAGRAM  OF  THE  SOLAR  SYSTEM. 

Showing    roughly    the    positions    of    the 

various  planets  and  their  moons. 


PROPERTIES   OF  MATTER  7 

All  matter  as  we  know  it  occupies  room  or  space.  In 
other  words,  it  has  extension.  When  we  pump  up  a  bi- 
cycle tire  we  find  that  even  the  air  demands  room  for 
itself.  In  the  experiment  with  the  air  compressor 
we  found  that  the  space  occupied  by  the  air  could  be  re- 
duced only  to  a  limited  extent.  However  great  the  pres- 
sure might  have  been  the  air  would  still  have  occupied  a 
certain  amount  of  space. 

Experiment  2.  —  Place  a  coin  on  a 
card  extending  slightly  beyond  the 
edge  of  a  table.  Suddenly  snap  the 
card  horizontally.  Does  the  coin  move  ? 

Another  of  our  common  observations  is  that  a  body 
does  not  begin  to  move  unless  some  force  acts  upon  it,  nor 
when  moving  does  it  stop  unless  some  force  stops  it. 
When  the  card  was  snapped  from  under  the  coin,  the  coin 
did  not  appear  to  move  because  the  friction  of  the  paper 
was  not  sufficient  to  transfer  any  appreciable  motion  to  it. 
If  the  coin  had  been  glued  to  the  card,  both  coin  and  card 
would  have  moved. 

Experiment  3.  —  Revolve  around  the  hand  a  small  weight  attached 
to  a  strong  rubber  baud.  Suddenly  let  go  the  band.  Does  the  weight 
keep  on  moving  in  the  circular  path  in  which  it  was  revolving? 

When  a  car  is  moving  along  a  level  track  we  do  not  ex- 
pect it  to  stop  until  the  friction  of  the  track  or  some  other 
force  stops  it.     When  we  revolved  the 
/'"  \.         weight   attached   to   the   rubber  band 

\  and  let  go  the  band  the  weight  started 
off  in  a  straight  line.  It  did  riot  con- 
tinue in  this  straight  line  because  a 
force,  gravity,  pulled  it  down  toward 

"""• — "'''  the  earth.    This  property  which  bodies 

2.  have     of    remaining     at     rest     unless 


\ 


8 


FIRST   YEAH   SCIENCE 


acted  upon  by  some  force;  and  when  in  motion  of  con- 
tinuing to  move  in  a  straight  line  with  the  same  speed, 
unless  acted  upon  by  £,n  outside  force, 
is  called  inertia.  Sir  Isaac  Newton 
first  stated  this  fact,  and  so  it  is  some- 
times called  Newton's  First  Law.  It 
is  the  force  of  inertia  which  throws 
one  out  of  an  automobile  if  it  is  sud- 
denly stopped. 

Experiment  4.  —  Suspend  a  heavy  ball  by  a 
string  not  much  too  strong  to  hold  it.  (Place 
a  pad  beneath  it  to  catch  it  if  it  drops.) 
Attach  a  similar  string  to  the  bottom  of  the 
ball.  Attempt  to  lift  it  suddenly  by  the  upper 
string.  What  happens?  Suspend  it  again 
and  pull  down  gradually  on  the  lower  string. 
What  happens?  Suspend  it  again  and  pull 
down  suddenly  on  the  lower  string.  What 
happens? 


Fig.  3. 


When  we  tried  suddenly  to  lift  the  suspended  ball  the 
force  of  inertia  was  so  great  that  it  broke  the  string. 
When  the  string  was  attached  to  the  bottom  of  the  ball 
and  the  pull  gradually  exerted,  the  upper  string  broke, 
since  it  had  both  the  weight  of  the  ball  and  the  pull  of 
the  string  to  withstand ;  but  when  the  pull  was  suddenly 
exerted,  the  inertia  of  the  ball  was  sufficient  to  withstand 
the  pull,  and  the  lower  string  broke. 

It  is  the  inertia  of  the  water  which  enables  the  small, 
rapidly  revolving  propeller  to  move  the  big  ship.  The 
same  is  true  of  both  the  propelling  and  supporting  of  fly- 
ing machines.  The  resistance  which  the  particles  of  air 
offer  to  being  suddenly  thrown  into  motion,  their  inertia, 
enables  the  propeller  to  push  the  aeroplane  along  and 
keeps  it  from  falling  to  the  ground  as  long  as  it  is  moving 
rapidly.  It  is  inertia  which  keeps  the  heavenly  bodies 


PROPERTIES   OF  MATTER 


A  BIPLANE. 
The  blur  shows  how  swiftly  the  propeller  is  revolving. 

moving   in   space.     Once  in  motion  they  must   keep  on 
forever  unless  some  force  stops  them. 

Experiment  6.  —  Place  a 
glass  globe  partly  filled  with 
water  on  a  rotating  appa- 
ratus. Rotate  the  globe 
rapidly.  What  does  the 
water  tend  to  do  ? 

Inertia  also  manifests 
itself  in  the  tendency 
of  revolving  bodies  to 
move  away  from  the 
center  around  which  they  are  revolving.  Inertia  thus 
manifesting  itself  is  called  centrifugal  force.  An  ex- 
ample of  this  was  seen  in  Experiments  3  and  5. 


1 


Fig.  4. 


10  FIRS T   YEAR   SCIENCE 

Newton  many  years  ago'  discovered  that  all  bodies  of 
matter  have  an  attraction  for  each  other  and  that  this 
force  of  attraction  varies  as  the  masses  of  the  bodies, 
that  is,  the  more  matter  two  bodies  contain  the  more  they 
attract  each  other.  But  this  attraction  becomes  less  as 
the  distance  between  the  bodies  increases.  This  lessening 
of  the  force  of  attraction  on  account  of  the  increase  of 
distance  is  proportional  not  to  the  distance,  but  to  the 
square  of  the  distance.  This  means  that  the  attraction 
between  the  same  bodies  when  twice  as  far  apart  is  only 
one  fourth  as  great;  when  three  times  as  far  apart,  one 
ninth  as  great,  and  so  on.  What  causes  this  attraction  no 
one  knows,  but  the  name  given  to  this  force  of  attraction 
is  Gravitation.  Gravitation  is  always  acting  upon  all 
bodies,  and  their  conduct  is  constantly  affected  by  it. 
It  keeps  the  heavenly  bodies  from  wandering  away  from 
each  other  just  as  the  rubber  band  kept  the  weight  from 
flying  away  from  the  hand. 

When  this  attraction  is  considered  in  relation  to  the 
earth  and  bodies  near  its  surface  the  term  gravity  is  used. 
We  are  constantly  measuring  the  pull  of  gravity  and  call- 
ing it  weight.  This  is  the  cause  of  bodies  falling  to  the 
earth.  It  is  the  force  which  causes  us  to  lie  down  when 
we  wish  to  sleep  comfortably,  and  frequently  makes  us  fall 
if  we  try  to  fly. 

If  two  forces  act  upon  a  free  body,  each  will  influence 
the  direction  of  its  motion  and  it  will  go  in  the  direction 
of  neither  force,  but  in  a  direction  between  the  two.  If 
there  are  more  than  two  forces,  the  path  will  be  the  result 
of  the  action  of  all  the  forces.  In  the  case  of  the  weight 
and  the  rubber  band  we  found  that  the  moving  weight 
when  not  held  by  the  force  of  the  band  flew  away  from 
the  hand.  The  rubber  band  continually  pulled  it  toward 
the  hand.  The  result  of  these  two  forces,  the  inertia 


RELATION   OF  EARTH    TO   SUN  AND  MOON 


11 


of  the  weight  and  the  pull  of  the  band,  was  to  make  the 
path  of  the  weight  lie  between  the  two.     In  this  case  the 

forces  at  every  instant 
almost  balanced  each 
other,  and  the  path  was 
nearly  a  circle.  It  is 
the  force  of  gravitation 
acting  against  the  iner- 
tia, or  the  centrifugal 


PUSH 


THREE  FORCES  IN  PLAY. 


Fig.  5. 


force,  of  the  heavenly  bodies  which  holds  them  in  their 
orbits. 

4.  Relation  of  the  Earth  to  Sun  and  Moon.  —  Not  only  do 
all  the  planets  revolve  around  the  sun,  but  certain  of  these 
themselves  have  other  smaller  bodies  revolving  around 
them.  We  call  such  small  bodies  satellites  or  moons.  The 
earth  has  one  of  these  satellites  and  Saturn  has  the  greatest 
number  of  all,  ten,  one  having  been  discovered  as  late  as 
1905.  Our  own  moon  has  a  diameter  of  about  2000  miles  and 
a  weight  of  about  -^  that  of  the  earth.  Its  average  distance 
from  the  earth  is  about  240,000  miles.  Compared  with  the 
distance  of  the  other  heavenly  bodies  it  is  indeed  very  near. 

The  sun,  although  a  near  neighbor  as  compared  with  the 
rest  of  the  stellar  community,  is  at  an  average  distance  of 
about  93,000,000  miles.  It  is  so  big  that  if  it  were  hollow 


12 


FIRST  YEAR   SCIENCE 


and  the  earth  were  placed"  at  its  center  with  the  moon  as 
far  away  as  it  now  is,  there  Vould  be  almost  as  great  a 
distance  between  the  moon  and  the  sun's  surface  as  there 
is  between  the  moon  and  the  earth.  A  good  way  to  get 
an  idea  of  the  relative  size  of  these  bodies  is  to  let  a  pencil 
dot  represent  the  moon,  a  circle  an  eighth  of  an  inch  in 


SURFACE  OF  THE  MOON. 
Showing  the  great  crater-like  depressions. 

diameter  the  earth,  and  a  circle  with  a  diameter  of  a  little 
more  than  thirteen  and  one  half  inches  the  sun. 

Both  the  sun  and  the  moon  are  of  the  greatest  interest 
to  us,  as  they  have  much  to  do  with  our  existence.  If  it 
were  not  for  the  sun,  we  should  have  almost  no  heat  or 
light  on  the  earth,  and  life  could  not  exist.  If  the  sun 
were  much  nearer,  it  would  be  too  hot  for  life  as  we  know 
it,  and  if  much  farther  away,  too  cold.  If  it  were  not  for 
the  moon,  the  beauty  and  variety  of  our  nights  would  be 


RELATION  OF  EARTH  TO   SUN  AND  MOON          13 


HIGH  TIDE  IN  NOVA  SCOTIA. 


largely  lacking,  and  we  should  have  no  tides  strong  enough 

to  •  sweep  clean  our  bays,  removing  the  sewage,  and  to 

help    vessels    over     the 

bars    into    some    of    our 

harbors.       If     the     dis- 
tance of  the  moon  were 

changed,   the   height    of 

the      tides     would     be 

changed,  and  this  would 

greatly  affect  our  coast 

towns. 

Although  we  see  the 

moon  as    a    very  bright 

object    at    night    for    a 

part  of  every  month,  yet 

it  has  no  light  of  itself, 

and  all  the  light  it  gives  us  is  reflected  from  the  sun. 

It  has  a  rough,  barren, 
rocky  surface,  full  of 
great  crater-like  depres- 
sions. As  far  as  known, 
it  has  no  air  or  water 
upon  it.  As  the  earth 
goes  around  the  sun, 
and  the  moon  around 
the  earth,  the  position  of 
these  three  in  relation 
to  each  other  is  con- 
stantly changing,  and  it 
is  these  changes  which 
give  us  the  varying 


Low  TIDE  AT  THE  SAME  PLACE. 
Showing  the  clean  swept  sea  floor. 

heights  of  the  tides  and 

the  different  phases  of  the  moon.    It  is  profitable  to  try  to 
picture  to  oneself  the  changing  phases  of  the  moon.     A 


14  FIRST   YEAR   SCIENCE 

good  way  to  do  this  is  to -carry  a  ball  around  a  bright 
light  and  observe  what  part  of  the  surface  is  illuminated 
in  the  different  positions. 


THE  PHASES  OF  THE  MOON. 
Showing  roughly  the  positions  of  the  sun,  moon,  and  earth. 

Summary.  —  We  have  seen  that  the  earth  is  one  of 
eight  planets  which  revolve  about  the  sun.  The  sun  and 
the  bodies  revolving  around  it  comprise  the  solar  system. 
The  fixed  stars,  which  we  see  only  at  night  because  of  the 
great  brilliancy  of  the  sun  in  the  daytime,  are  suns  and 
may  —  like  our  sun  —  be  the  centers  of  separate  solar  sys- 
tems. 

Everything  in  the  universe  is  composed  of  matter,  which 
has  certain  definite  properties,  like  extension,  inertia,  gravi- 
tation, and  so  on.  The  action  of  some  of  these  properties 
maintains  the  relation  of  the  different  heavenly  bodies  — 
keeps  the  earth  revolving  around  the  sun  and  the  moon 
around  the  earth. 

The  sun  and  the  moon  have  more  influence  upon  the 


SUMMARY  15 

earth  than  do  any  other  bodies.  The  sun  gives  us  energy 
in  the  form  of  light  and  heat  and  so  maintains  all  the  life 
upon  the  earth.  The  moon,  though  shining  only  by  light 
reflected  from  the  sun,  exerts  a  great  attraction  upon  the 
earth,  causing  the  tides,  which  help  to  keep  the  waters 
of  our  harbors  clean. 

QUESTIONS 

Why  do  we  see  no  stars  in  the  daytime? 

How  is  the  appearance  of  the  stars  explained  ? 

What  is  the  difference  between  stars  and  planets? 

Wrhat  starlike  bodies  make  up  the  solar  system  ? 

Name  and  illustrate  three  universal  properties  of  matter. 

What  daily  experiences  of  yours  are  explained  by  these  properties  ? 

What  forces  keep  the  moon  moving  around  the  earth  in  its  orbit? 

Draw  circles  illustrative  of  the  size  of  the  earth,  moon,  and  sun. 

Why  are  the  sun  and  moon  particularly  interesting  to  us? 

How  long  would  it  take  an  express  train  running  thirty  miles  an 
hour  and  stopping  neither  day  nor  night  to  go  over  the  distance  from 
the  earth  to  the  moon  ?  From  the  earth  to  the  sun  ? 


CHAPTER    II 
THE  PLANET  EAKTH 

5.  The  Shape  of  the  Earth.  —  Men  who  have  in  different 
ways  made  careful  measurements  of  the  shape  of  the  earth 
tell  us  that  it  is  an  oblate  spheroid  (Fig.  6),  that  is,  a 
sphere  which  is  somewhat  flattened  at 
two  opposite  points.  An  ordinary 
orange  has  this  shape.  The  earth  has 
been  so  little  flattened,  however,  that 
its  shape  is  very  much  nearer  that  of 
a  perfect  sphere  than  is  that  of  an 
orange.  Its  polar  diameter  is  only  27 
miles  shorter  than  its  equatorial  di- 
ameter, so  when  we  consider  that  each  of  its  diameters 
is  nearly  8000  miles,  a  shortening  of  only  27  miles  in 
one  of  these  would  not  change  its  shape  from  that  of  a 
sphere  enough  to  be  noticed  except  by  the  most  care- 
ful measurements. 

• 

Experiment  6.  —  Attach  a  centrifugal  hoop  to  a  rotator  apparatus 
and  revolve.  The  hoop  bulges  at  the  center  or  point  of  greatest  mo- 
tion and  flattens  at  the  top  and  bottom  or  points  of  least  motion. 
The  earth  revolves  in  a  way  similar  to  the  hoop  and  is  very  slightly 
flattened  at  the  poles. 

Although  some  of  the  mountains  of  the  earth  rise  above 
sea  level  to  a  height  of  over  five  miles,  and  there  are 
depths  in  the  sea  which  are  somewhat  deeper  than  this 
below  sea  level,  yet  these  distances  are  so  little  in  com- 
parison to  the  size  of  the  earth  that  the  surface  is  com- 
paratively less  irregular  than  that  of  an  orange. 

16 


THE  SHAPE  OF  THE  EARTH 


17 


31614  n>5EA  LEVEL 


-  SOre  FT  =^=^-=  ~  ^5^5=1= 


In  these  days  many  men  have  sailed  around  the  earth, 
but  valiant  indeed  was  that  little  company  which  in  1522 
first  proved  that  it  was  possible  to  sail  continually  in  one 
direction  and  yet  reach  the  home  port,  thus  first  demon- 
strating that  the  earth  • 
was  globular.  Long  be- 
fore, wise  men  had  come 
to  believe  that  the  earth 
was  a  sphere,  for  it  had 
been  noted  as  far  back 
as  the  time  of  Aristotle, 
the  famous  Greek  phi- 
losopher, that  when  the 

Shadow  Of  the  earth  falls  MOUNT  EVEREST. 

upon  the  moon,  causing    As  !t  would  appear  if  Placed  in  the  deePest 

part  of  the  sea. 

an  eclipse  of  the  moon, 

the  boundaries  of  the  shadow  were  curved  lines.  It  was 
also  later  noticed  that  when  ships  are  seen  approaching 
at  sea  the  masts  appear  first  and  then  gradually  the  lower 
parts  of  the  ship.  The  reverse  was  seen  to  be  true  when 
ships  sailed  away. 

Experiment  7.  —  Add  alcohol  to  water  until  a  solution  is  obtained 
in  which  common  lubricating  oil  will  float  at  any  depth.  Insert  with 
a  glass  tube  a  large  drop  of  oil  below  the  surface  of  the  solution. 
The  oil  will  float  in  the  solution  in  the  shape  of  a  sphere.  This  illus- 
trates the  fact  that  if  a  liquid  is  relieved  from  the  action  of  outside 
forces,  it  will  take  the  form  of  a  perfect  sphere. 

A  spherical  surface  is  the  smallest  surface  by  which  a 
solid  can  be  bounded,  so  the  maximum  distance  which 
can  separate  places  located  on  a  given  solid  will  be  least 
when  its  surface  is  spherical.  Thus  the  inhabitants  of 
the  earth,  considering  the  surface  over  which  they  may 
scatter  themselves,  are  brought  into  the  closest  possible 
relation  to  one  another.  One  of  the  most  noteworthy 


18  FIRST  YEAR   SCIENCE 

consequences  of  the  earth's:  shape  is  the  ease  with  which 
knowledge,  news,  and  the  products  of  both  agriculture  and 
manufacture  are  carried  between  its  most, distant  parts. 

6.  The  Size  of  the  Earth.  —  It  is  easy  to  say  that  the 
polar  diameter  of  the  earth  is  7900  miles,  its  equatorial 
diameter  7927  miles,  and  its  equatorial  circumference 
24,902  miles,  but  a  true  conception  of  these  distances  is 
not  so  easy.  There  are,  however,  distances  on  the  surface 
of  the  earth  over  which  we  have  passed  and  about  which 
we  have  real  knowledge  ;  and  if  we  can  translate  other 
distances  into  terms  of  these,  then  the  unfamiliar  distances 
will  become  appreciable. 

One  of  the  best  ways  to  do  this  is  to  draw  a  line  which 
shall  represent  our  known  distance  and  then  with  this  as 

BOSTON    TO     CHICAGO     IOOO     MILES 


DIAMETER     OF     EARTH     8OOO     MILES 


CIRCUMFERENCE      OF      EARTH       25QOO      MILES 

Fig.  7. 

a  measure  draw  other  lines  which  shall  represent  the  dis- 
tances of  which  we  wish  to  get  an  appreciation.  Using 
as  our  standard  any  distance  with  which  we  are  really 
acquainted,  we  shall  find  that  the  lines  representing  the 
different  dimensions  of  the  earth  are  very  long.  How 
vastly  greater,  then,  must  be  the  distances  which  were 
mentioned  when  treating  of  the  stars. 

7.  Effect  on  Life  of  the  Irregularities  of  the  Earth's  Exterior. 
—  Although  the  irregularities  of  the  surface  of  the  earth, 
when  considered  in  relation  to  its  size,  are  insignificant, 
yet  in  relation  to  the  size  of  the  men  and  animals  that 
dwell  upon  the  earth  they  are  very  great.  Some  of  the 
mountains  rise  to  heights  that  are  inaccessible,  and  the 
oceans  in  some  places  sink  to  depths  which  until  recently 


THE  SHAPE  OF  THE  EARTH 


19 


were  immeasurable.  The  lofty  mountains  and  broad 
oceans  are  barriers  which  plants  and  animals  have  tried  in 
vain  to  cross  and  which  man  himself  has  had  difficulty  in 
surmounting. 


THE  HIMALAYA  MOUNTAINS. 
An  insurmountable  barrier  in  central  Asia. 

These  regions  have  furnished  protected  spaces  to  differ- 
ent species  of  plants,  groups  of  animals,  communities  of 
men,  and  unmolested  in  these  protected  places  they  have 
developed  their  peculiar  characteristics.  Where  man  has 
not  succeeded  in  thoroughly  overcoming  the  barrier,  se- 


20  FIRST   YEAR   SCIENCE 

>.'**•  i* 

eluded  and  unprogressive  peoples  are  still  to  be  found. 

Such  are  the  Highlanders  of  Scotland  and  of  our  own  Ap- 
palachian plateau.  The  gentler  inequalities  of  the  earth's 
surface  have  by  their  lakes  and  rivers  afforded  easy  means 
of  transportation  from  one  community  to  another  and  have 
opened  paths  into-  hitherto  unexplored  regions.  These 
waterways  have  been  from  the  earliest  times  arteries  of 


A  COTTAGE  IN  THE  SCOTCH  HIGHLANDS. 

commerce  and  progress,  and  largely  through  them  have 
the  interior  lands  been  colonized  and  developed. 

Where  great  plains  and  plateaus  stretch  their  broad  and 
level  surfaces  over  vast  areas,  plants,  animals,  and  men  for 
ages,  unimpeded  by  natural  barriers,  have  been  thrown  to- 
gether and  have  striven  unrelentingly  for  mastery.  They 
have  here  developed  into  great  aggregations,  not  into  small 
distinct  communities.  Here  there  has  been  no  shelter  for 
the  weaker  group  except  as  its  identity  was  lost  in  merg- 
ing with  the  mass. 


THE  INTERIOR   OF  THE  EARTH  21 

8,  The  Interior  of  the  Earth.  —  Whenever  borings  have 
been  made  into  the  interior  of  the  earth  it  has  been  found, 
after  a  depth  had  been  reached  where  there  was  no  effect 
from  the  heat  of  the  sun,  that  the  temperature  rose  as  the 
boring  increased.     From  this  gradual  increase  of  tempera- 
ture, it  must  be  that  far  down  within  the  earth  the  tem- 
perature is  very  high.     The  pressure  within  the  earth  is 
so  great,  however,  that  there  are  probably  no  liquid  rocks 
at  great  depths.     If  the  earth  had  a  liquid  interior  the 
attraction  of  the  bodies  about  it  in  space  would  cause 
changes  in  its  shape,  but  it  is  as  rigid  as  steel. 

The  outside  cold  part  of  the  earth  is  called  its  crust. 
How  thick  this  is  no  one  knows.  This  is  the  part  that  is 
of  particular  interest  to  us,  for  it  is  the  only  part  which 
we  are  able  to  observe  and  study. 

9,  The  Cause  of  Day  and  Night.  —  Experiment  8.— (a)  In  a 
darkened  room  place  a  globe  a  short  distance  from  a  small  but  strong 
light.     Revolve  the  globe  with  its  axis  at  right  angles  to  the  line 
which  joins  the  centers  of  the  globe  and  light.     How  mueh  of  the 
globe  is  illuminated  by  the  light  ?    Is  the  same  part  of  the  globe  il- 
luminated all  the  time?     Does  any  place  on  the  illuminated  part  re- 
ceive light  for  a  longer  time  during  a  revolution  than  any  other  place  ? 
Remove  the  globe  to  the  opposite  side  of  the  light  without  changing 
the  direction  of  its  axis.     When  revolved,  is  there  any  change  in  the 
globe's  illumination?     If  so,  what? 

(&)  Now  make  the  axis  on  which  the  globe  revolves  parallel  to 
the  line  joining  the  centers  of  the  globe  and  light.  Revolve  the  globe. 
How  much  of  the  globe  is  illuminated  by  the  light?  Is  the  same 
part  illuminated  all  the  time  ?  Does  any  place  on  the  illuminated 
part  receive  light  for  a  longer  time  during  a  revolution  than  any 
other  place  ?  Removte  the  globe  to  the  opposite  side  of  the  light 
without  changing  the  direction  of  its  axis.  When  revolved  is  there 
any  change  in  the  globe's  illumination  ?  If  so,  what  ? 

(c)  Place  the  axis  of  the  globe  so  that  it  is  inclined  to  the  line 
joining  the  centers  of  the  globe  and  light.  Revolve  the  globe.  How 
much  of  the  globe  is  illuminated?  Is  the  same  part  of  the  globe  il- 
luminated all  the  time?  Do  any  places  in  the  illuminated  part  re- 


22 


FIRST   YEAR    SCIENCE 


ceive  light  for  a  longer  time  during  a  revolution  than  other  places  ? 
Remove  the  globe  to  the  opposite  side  of  the  light  without  changing 
the  direction  of  its  axis.  When  the  globe  is  revolved  is  there  any 
change  in  the  length  of  time  of  illumination  of  the  places  before  noted? 
If  so,  what? 

As  has  already  been  stated,  the  ancients  considered  the 
earth  as  the  center  of  the  universe  and  thought  that  the 

sun  and  stars  revolved 
around  it.  We  of  the 
present  day,  however, 
know  that  it  is  the  ro- 
tation of  the  earth  from 
west  to  east  that  causes 
the  appearance  of  the 
rising  and  setting  sun 
and  thus  makes  day  and 
night. 

Of  course  it  makes  no 
difference  about  a  person 
beginning  to  see  a  light 
whether  the  light  is 
brought  toward  him  or 
whether  he  goes  toward 
the  light.  We  are  turned 
into  and  out  of  the  sun- 
light by  the  rotation  of 
the  earth.  We  speak  of  the  sun  as  rising  high  in  the 
sky,  but  what  really  happens  is  that  we  are  turned  so 
that  the  center  of  the  earth,  our  heads  and  the  sun  come 
nearer  and  nearer  toward  a  straight  line. 

When  we  say  down  we  mean  toward  the  center  of  the 
earth,  and  when  we  say  up  we  mean  in  the  opposite  direc- 
tion. These  are  the  only  two  directions  that  we  could  be 
easily  sure  of,  if  it  were  not  for  the  rotation  of  the  earth. 


MEDIEVAL  IDEA  OF  THE  UNIVERSE. 

From  a  fourteenth-century  manuscript. 
Above  the  earth  are  the  clouds  and  the 
moon ;  then  the  rays  of  the  sun ;  next 
various  planets ;  above  these  the  stars ; 
and  finally  the  signs  of  the  zodiac. 


MOVEMENT   OF  THE  EARTH  23 

This  gives  the  direction  of  the  rising  sun,  which  we  call 
east,  and  of  the  setting,  which  we  call  west.  A  line  which 
runs  at  right  angles  to  the  one  joining  east  and  west,  i.e. 
one  running  parallel  to  the  axis  of  the  earth,  is  said  to  run 
north  and  south.  Thus  the  points  of  the  compass,  as  well 
as  day  and  night,  are  determined  for  us  by  the  earth's  rota- 
tion. The  north  star,  which  is  so  important  to  the  sailor 
in  determining  his  direction,  is  simply  a  star  which  is 
almost  in  line  with  the  axis  of  the  earth.  It  is  the  rota- 
tion of  the  earth  which  gives  us  also  our  means  of  measur- 
ing time. 

As  was  seen  in  the  previous  experiment,  the  direction  of 
the  axis  of  a  revolving  globe  has  much  to  do  with  the  light 
which  different  parts  of  it  will  receive  from  a  luminous 
object.  The  hemisphere  which  is  inclined  toward  the 
luminous  object  will  have  a  larger  part  of  its  surface 
illuminated  and  therefore  each  place  on  it  will  be  longer 
in  the  light  during  5?  revolution  than  when  the  hemisphere 
is  inclined  in  the  opposite  direction. 

As  the  axis  of  the  earth  is  inclined  to  a  line  drawn  from 
the  earth  to  the  sun,  the  light  the  earth  receives  is  similar 
to  that  received  by  the  globe  in  the  last  part  of  the  experi- 
ment. Thus  the  days  and  nights  vary  in  length  during 
the  year,  because  in  summer  the  northern  hemisphere  is 
inclined  toward  the  sun  and  in  winter  away  from  it. 

10.  The  Movement  of  the  Earth  around  the  Sun.  — The  earth 
not  only  turns  on  its  axis  every  day,  but  it  travels  around 
the  sun  in  a  direction  opposite  to  the  motion  of  the  hands 
of  a  watch.  It  moves  with  the  tremendous  average  velocity 
of  about  19  miles  a  second.  It  is  this  revolution  around 
the  sun  which  gives  us  our  measure  of  time  which  we  call 
a  year.  It  takes  365  days  and  a  fraction  to  complete  this 
revolution,  so  we  consider  365  days  to  be  a  year,  and  add  a 
day  practically  every  fourth  year  to  make  up  the  fraction. 


24  FIRST   YEAR   SCIENCE 

*  /* 

In  the  journey  around  the  sun  the  earth  does  not  move 

in  a  circle  but  in  an  ellipse,  which  is  a  figure  something 

like  a  circle,  but  having  one 
of  its  diameters  longer  than 
the  other.  This  figure  can 
be  drawn  by  sticking  two 
pins  into  a  piece  of  paper,  a 
little  distance  apart,  and 
tying  to  each  pin  one  end  of 
a  string,  the  length  of  which 
is  several  times  the  distance 

!-••  Q 

between  the  pins.  Then  put 

a  pencil  into  the  loop  of  the  string  and  draw  the  curve 
which  will  be  formed  on  either  side  of  the  pins  by  the 
pencil  being  moved  over  the  paper  in  the  extended  loop. 

The  points  where  the  pins  pierce  the  paper  are  called  the 
foci,  and,  as  will  be  seen,  each  of  these  points  is  nearer  one 
half  of  the  curve  than  the  other.  If  af  body  were  placed  at 
one  of  these  points  and  another  body  moved  around  it  in 
the  line  of  the  curve,  the  two  bodies  would  be  nearest  each 
other  when  passing  one  point  in  the  line  extending  through 
the  foci,  and  farthest  apart  when  passing  the  opposite  point 
in  the  same  line. 

Now  the  sun  is  at  one  of  the  foci  of  the  ellipse  in  which 
the  earth  moves,  so  the  distance  between  the  sun  and  the 
earth  varies  during  the  year.  This  variation  is  about 
three  millions  of  miles,  the  average  distance  of  the  earth 
from  the  suri  being  about  93,000,000  miles.  Strange  as  it 

94,500,OOOMILE5  -^s£     9I,5OO,OOQM  I  LES 

SUMMER  WINTER 

Fig.  9. 

may  seem,  we  are  nearest  the  sun  in  January  and  farthest 
away  in  July  (Fig.  9).  We  are  not  warmest  in  the  north- 


LATITUDE  ZONES 


25 


NORTH  POLE 


ern  hemisphere  in  January  because  our  hemisphere  is  then 
pointed  away  from  the 
sun  and  therefore  there 
are  fewer  heat  rays  fall- 
ing upon  a  given  area 
in  this  hemisphere  than 
there  are  when  we  are 
farther  away  in  July. 

11.  Latitude  Zones.  — 
As  the  axis  of  the  earth 
is  inclined  23J°  from 
the  perpendicular  to  the 
plane  of  its  orbit,  the 
rays  of  the  sun  will  fall 


// 

7 

1 

\ 

\ 

\\ 

' 

EQUATOR 

1 

* 

\\  \  1 

/ 

// 

SGUTH  POLE 
Fig.  10. 


vertically  at  some  times 

during  a  year  upon  all 

points  within  23 J°  of  the  equator  both  north  and  south. 

To  this  region  we  have 
given  the  name  of  the 
torrid  zone.  There  will 
be  a  day  during  the 
year  when  no  direct 
sunlight  will  fall  upon 
points  within  23J°  of 
the  poles.  The  areas 
inclosed  by  lines  drawn 
around  the  earth,  23J° 
from  the  poles,  are 
called  frigid  zones.  The 
areas  between  the  frigid 
zones  and  the  torrid 
called  the 


A  LAPLANDER'S  HUT. 

Made  of  thick  sod  to  keep  out  the  cold 

of  the  frigid  zone. 

zones     are 

temperate  zones.     We  live  in  the  north  temperate  zone. 
Although  as  far  as  the  direct  influence  of  the  sun  is  con- 


26 


FIRST   YEAR   SCIENCE 


MARCH  CQUINDX 


cerned,  these  zones  are  easily  separated  and  bounded  by 
parallels  of  latitude,  yet,  on  account  of  other  influences, 
the  temperatures  of  the  zones  thus  bounded  are  very  ir- 
regular. For  instance,  at  some  places  like  Hammerfest 
within  the  frigid  zone  the  average  temperature  is  much 
higher  than  at  places  like  Labrador  within  the  temperate 
zone,  so  that  as  regards  temperature,  the  parallels  of 
latitude  are  uncertain  boundaries.  This  will  be  more  fully 
discussed  later. 

12.  The  Cause  of  the  Seasons.  —  Since  the  earth  moves 
around  the  sun  with  its  axis  inclined  to  the  plane  of  its  orbit, 

the  hemispheres  will  at 
different  times  be  in- 
clined toward  and  away 
from  the  sun.  When 
the  northern  hemisphere 
is  inclined  toward  the 
sun,  the  rays  of  the  sun 
cover  the  north  pole 
continuously  for  six 
months,  so  that  at  this 
point  there  is  no  night 
for  all  that  time.  The 
days  are  longer  and  the 

nights  shorter  throughout  all  the  northern  hemisphere, 
and  more  than  this,  the  rays  then  fall  upon  this  hemisphere 
more  nearly  vertically  than  during  the  rest  of  the  year. 

The  nearer  vertical  the  rays,  the  greater  the  number 
that  fall  upon  a  given  area  and  the  greater  the  amount  of 
heat  received  by  that  area.  More  heat  is  received  in  the 
northern  hemisphere  not  only  because  the  rays  fall  more 
nearly  vertically  but  also  because  the  length  of  the  day 
is  increased.  The  amount  of  heat  received  from  the  sun 
continues  to  increase  as  long  as  the  sun  appears  to  move 


SEPTEMBER  EQUINOX 
THE  PATH  OF  THE  EARTH  AROUND  THE 

SUN. 

Showing  roughly  the  four  positions  men- 
tioned in  the  text. 


CAUSE  OF  THE  SEASONS 


27 


north,  or  until  its  rays  fall  vertically  upon  the  tropic  of 
Cancer.  This  occurs  on  the  21st  of  June,  which  is  called 
the  summer  solstice.  At  this  time  our  days  are  the  longest 
and  our  nights  the  shortest.  But  the  days  are  not  the 
hottest,  as  the  heat  gradually  accumulates  for  some  time, 
more  being  received  each  day  than  is  given  off. 

As  the  earth  proceeds  in  its  orbit  from  this  point,  the 
inclination  of  the  north  pole  toward  the  sun  becomes  less 


HUT  IN  THE  TROPICS. 
Made  of  thin  walls  but  a  heavy  thatched  roof  to  keep  out  the  rain. 

and  less,  until  on  the  23d  of  September  the  sun  is  directly 
over  the  equator.  The  north  pole  now  begins  to  point 
away  from  the  sun.  On  December  21  the  direct  rays  of 
the  sun  fall  upon  the  tropic  of  Capricorn,  and  the  sun  has 
reached  its  farthest  point  south,  our  days  being  then  the 
shortest  and  the  days  in  the  southern  hemisphere  the 
longest.  From  this  point  until  March  21,  when  the  sun  is 


28  FIRST   TEAR   SCIENCE 

4<* 

again  vertical  over  the  equator,  the  inclination  of  the  north 
pole  away  from  the  sun  decreases.  The  days  when  the 
sun  is  over  the  equator  are  called  the  autumnal  (Sept.  23) 
and  vernal  (March  21)  equinoxes,  since  the  days  and  nights 
are  then  of  equal  length  all  over  the  earth. 

The  greater  heating  of  the  hemisphere  at  one  part  of  the 
year  than  at  another  gives  us  the  changes  which  we  call 
the  seasons.  Since  the  change  in  the  length  of  the  day 
and  in  the  direction  of  the  sun's  rays  is  very  small 
within  the  tropics,  the  change  in  the  amount  of  heat 
received  is  very  slight,  so  that  in  this  region  there  is 
almost  no  change  of  seasons.  But  at  the  poles,  where 
for  six  months  there  is  continuous  night  and  for  six 
months  continuous  day,  the  change  of  seasons  is  exceed- 
ingly great.  At  middle  latitudes  the  changes,  though 
marked,  are  not  excessive. 

There  are  then  two  causes  which  combine  to  give  us  our 
change  of  seasons:  the  revolution  of  the  earth  around  the 
sun,  and  the  inclination  of  the  earth's  axis  to  the  plane  of 
its  orbit. 

13.  The  Measurement  of  Time.  —  Experiment  9.  — On  a  fair 
day  place  a  sundial  in  an  exposed  position,  and  after  carefully  adjust- 
ing it,  compare  its  readings  with  those  of  an  accurate  watch.  Prob- 
ably your  watch  is  set  to  railroad  time  and  the  readings  therefore  are 
not  alike,  unless  you  are  on  the  time  meridian. 

Although  the  exact  determination  of  time  is  a  difficult 
task  and  requires  great  skill  and  very  accurate  instru- 
ments, yet  it  is  not  very  hard  to  determine  quite  satis- 
factorily the  length  of  a  solar  day.  Before  there  were  any 
clocks,  people  told  the  time  of  day  by  sundial  (Fig.  11), 
which  consisted  of  a  vertical  rod,  the  shadow  of  which 
fell  upon  a  horizontal  plane.  From  local  noon,  or  the 
time  the  sun  cast  the  shortest  shadow  on  a  certain  day, 


MEASUREMENT  OF  TIME 


29 


until  it  cast  the  shortest  shadow  the  next  day,  was  con- 
sidered a  day's  time,  or  a  solar  day,  and  was  divided  into 
twenty-four  equal  parts 
called  hours. 

The  direction  of  the 
shortest  shadow  is  a 
north  and  south  line, 
since  the  sun  must  then 
be  halfway  between  the 
eastern  and  western 
horizon .  As  the  1  engths 
of  these  solar  days  vary 
slightly,  for  •  reasons 


which    cannot    be    ex- 


Fig.  11. 


plained  here,  we  now  divide  the  mean  length  of  the  solar 
days  for  the  year  into  24  parts  to  get  the  hours.  The 
civil  or  conventional  day  begins  at  midnight,  not  noon. 
The  determination  of  the  exact  time  is  very  important ; 
for  the  United  States  it  is  done  at  the  Naval  Observatories 
at  Washington  and  at  Mare's  Island,  San  Francisco,  and 
telegraphed  each  day  to  different  parts  of  the  country. 

A  day  may  be  measured  by  the  interval  between  the  suc- 
cessive passages  of  a  star  across  the  zenith.  This  would 
be  called  a  sidereal  day,  from  the  Latin  word  for  star.  It 
might  also  be  measured  by  successive  passages  of  the 
moon  across  the  zenith.  This  would  be  called  a  lunar 
day,  from  the  Latin  word  for  moon. 

If  a  person  should  start  at  noon  and  travel  around  the 
earth  from  east  to  west  as  fast  as  the  sun  does,  the  sun 
would  be  overhead  all  the  time  and  no  solar  day  would 
have  passed  for  the  traveler,  even  though  24  hours  would 
be  required  for  the  trip.  But  when  he  reached' home  he 
would  find  that  it  was  the  next  day.  Thus  any  one  travel- 
ing around  the  earth  must  skip  a  day  if  going  toward  the 


30 


FIRST   YEAR   SCIENCE 


west  and  add  a  day  if  going  toward  the  east.  The  con- 
ventional place  where  this  is  done  is  at  the  International 
Date  Line,  a  line  extending  through  tfye  Pacific  Ocean 
and  in  general  corresponding  with  the  180th  meridian. 


MAP  SHOWING  INTERNATIONAL  DATE  LINE  (Dotted  Line). 

14.  Standard  Time.  —  When  railways  extending  east  and 
west  became  numerous  in  the  United  States  and  there 
were  many  through  trains  and  numerous  passengers,  it 
became  very  inconvenient  to  use  local  time,  since  no  two 
places  had  the  same  time.  Each  railway  therefore  adopted 
a  time  of  its  own,  and  when  several  railways  entered  the 
same  city  these  different  times  became  very  confusing. 
Therefore  in  1883  the  American  Railway  Association  per- 
suaded the  Government  to  adopt  Standard  Time. 


STANDARD   TIME 


31 


A  certain  meridian  was  adopted  as  the  time  meridian 
for  a  definite  belt  of  country.  The  meridians  adopted 
were  75°  for  Eastern,  90°  for  Central,  105°  for  Mountain, 
120°  for  Pacific  Time.  These  meridians  run  through  the 
centers  of  the  time  belts  and  for  7-J°  on  either  side  the 
time  used  is  the  local  time  of  the  central  meridian. 
When  a  person  crosses  from  one  belt  to  another  he  finds 
that  the  time  makes  an  abrupt  change  of  an  hour.  This 
system  has  been  extended  to  all  the  United  States  posses- 


MAP  SHOWING  STANDARD  TIME  BELTS. 

sions,  and  is  coming  into  general  use  over  a  large  part  of 
the  world.  In  actual  practice  the  changes  of  time  are  not 
made  where  the  boundaries  of  the  time  belts  are  crossed, 
but  at  important  places  near  these. 

Experiment  10.  —  On  a  day  when  there  appear  to  be  indications  of 
settled  fair  weather  place  a  table  covered  with  blank  paper  in  an 
open  space  where  the  sun  can  shine  upon  it.  Make  the  top  of  the 
table  level  and  fix  it  firmly  so  that  it  cannot  be  moved.  Fix  vertically 
upon  the  table  a  knitting  needle  or  a  slender  stick.  Mark  the  line  of 


32 


FIRST   YEAR   SCIENCE 


the  sun's  shadow  and  note  accurately  the  time  the  shadow  fell  on  this 
line.  On  the  next  day  note  the  time  the  shadow  falls  upon  the  same 
line.  If  your  watch  is  right,  the  difference  in  time  it  shows  between 
the  falling  of  the  shadows  the  first  and  the  seconcl  days  is  the  differ- 
ence between  this  particular  solar  day  and  the  mean  solar  day.  This 
may  be  nearly  a  minute.  The  shortest  shadow  of  the  day  marks 
noon.  It  extends  north  and  south.  (Your  watch  keeps  mean  solar 
time.  But  twelve  o'clock  by  your  watch  will  probably  not  be  mid- 
day or  high  noon,  as  your  watch  is  set  to  Standard  Time.) 

15.  Meridians  and  Parallels  of  Latitude.  —  For  purposes 
of  measurement,  circles  of  any  size  are  divided  into  360 
equal  parts  called  degrees.  Thus  the  equatorial  circle  of 

the  earth  is  divided  into  360 
parts.  Through  each  of  these 
divisions  there  is  a  semicircle 
drawn  from  pole  to  pole.  These 
semicircles  are  called  meridians. 
Each  meridian  is  divided  into 
180  parts  called  degrees  of  lati- 
tude, and  through  these  points 
of  division  are  passed  circles 
parallel  to  the  equator.  These 
circles  gradually  decrease  in  size 
as  they  approach  the  poles.  They  are  called  parallels  of 
latitude  and  are  numbered  from  0  at  the  equator  to  90  at 
the  poles. 

A  certain  one  of  the  meridians,  usually  the  one  passing 
through  Greenwich,  England,  is  called  the  prime  meridian 
and  numbered  0.  East  and  west  of  this  the  meridians  are 
numbered  from  1  to  180.  The  degrees  thus  numbered  are 
called  degrees  of  longitude.  Thus  we  have  a  skeleton  out- 
line by  means  of  which  we  are  easily  able  to  locate  the 
position  of  any  place  upon  the  earth.  To  secure  greater 
accuracy  than  could  be  obtained  by  giving  merely  the 
degrees  of  latitude  and  longitude,  each  of  these  degrees  is 


12. 


DETERMINATION  OF  LONGITUDE  33 

divided  into  60  equal  parts  called  minutes,  and  each  minute 
can  be  divided  into  60  parts  called  seconds. 

It  will  be  seen  at  once. that  the  lengths  of  the  degrees 
of  longitude  decrease  as  the  pole  is  approached,  since  all 
the  meridians  pass  through  the  poles  and  the  distance  be- 
tween the  meridians,  which  is  considerable  at  the  equator, 
becomes  nothing  at  the  poles.  Of  course  these  lines  are 
simply  imaginary  lines  and  do  not  really  exist,  but  in 
making  a  map  or  a  globe  we  draw  them  as  if  they  existed. 
The  length  of  a  degree  of  latitude  at  the  equator  is  68.7 
miles,  at  the  poles,  69.4.  The  difference  is  due  to  the 
flattening  of  the  earth  near  the  poles.  The  length  of  a 
degree  of  longitude  at  the  equator  is  69.65  miles,  at  the 
poles,  0. 

16.  Determination  of  Longitude.  —  Since  the  earth  turns 
on  its  axis  once  in  24  hours,  the  interval  between  the  pas- 
sage of  successive  meridians  under  the  sun  will  be  four 
minutes  (24  x  60  -5-  360  =  4).  At  a  point  one  degree 
east  of  us  the  noon  by  local  time  is  four  minutes  earlier 
than  it  is  with  us,  and  at  one  degree  west  it  is  four  min- 
utes later.  *If  an  accurate  clock  were  set  to  twelve  o'clock 
when  the  sun  was  nearest  vertical  at  a  certain  place, 
and  were  then  carried  to  a  place  15°  west,  it  would 
indicate  one  o'clock  at  the  more  western  locality  when  it 
was  noon  at  the  first  place.  Or,  changing  the  statement, 
if  the  clock  indicated  one  o'clock  when  the  sun  reached 
the  highest  point,  the  place  must  be  15°  west  of  the 
place  from  which  the  clock  started. 

Thus  we  see  that  by  means  of  an  accurate  timekeeper 
we  can  tell  difference  of  longitude  between  different 
places.  Every  sea  captain  is  provided  with  one  or  more 
accurate  clocks  called  chronometers,  which  are  usually  set 
to  the  time  at  Greenwich.  Thus  all  he  needs  to  do  to 
get  the  difference  in  degrees  of  longitude  between  his 


34  FIRST   TEAR   SCIENCE 

1  .  -<* 

position  and  Greenwich  is  to  determine  when  the  sun  has 
reached  its  highest  point  and  to  multiply  by  fifteen  the 
difference  in  hours  between  the  time  as  shown  by  the 
chronometer  and  twelve  o'clock.  If  the  chronometer  is 
too  slow  he  is  east,  and  if  too  fast,  west,  of  Greenwich. 

The  determination  of  latitude  is  more  difficult,  but  can 
be  easily  done  by  one  knowing  how  and  having  the  proper 
instrument.  The  manner  of  its  determination  is  described 
in  the  appendix. 

17.  Magnetism  of  the  Earth.  —  There  is  a  peculiar  prop- 
erty of  the  earth  which  has  been  of  the  greatest  assistance 
to  geographical  explorers  and  without  which  it  would  be 
very  difficult  to  find  a  way  over  the  sea.  This  property 
is  called  terrestrial  magnetism.  In  very  ancient  times 
pieces  of  iron  ore  were  found  which  had  the  property 
of  attracting  iron.  Such  pieces  of  ore  are  called  load- 
stones. Artificial  loadstones  are  called  magnets.  If  a  bar 
of  loadstone  or  a  magnetic  needle  is  floated  in  a  basin  of 
water,  or  if  freely  suspended,  it  will  invariably  assume  a 
definite  position. 

This  discovery  was  made  in  the  far  east  at  a  very  early 
date,  but  it  was  put  to  no  particular  use  in  the  sailing  of 
ships  until  about  the  middle  of  the  thirteenth  century. 
Since  then  it  has  enabled  sailors  to  go  far  out  from  the 
sight  of  land  and  yet  always  to  know  the  direction  in  which 
they  are  going.  It  was  supposed  even  up  to  the  time  of 
the  first  voyage  of  Columbus  that  the  magnetic  needle 
always  pointed  toward  the  north  star  or  perhaps  at  some 
places  a  little  to  the  east  of  it,  and  the  sailors  of  Columbus 
were  greatly  alarmed  when  they  found  as  they  sailed  west 
that  the  needle  swung  off  to  the  west  of  the  true  north. 

This  difference  in  the  direction  of  the  needle  from  a  true 
north  and  south  line  is  called  the  declination.  The  west- 
ward declination  was  one  of  the  great  discoveries  of 


MAGNETISM  OF  THE  EARTH 


35 


Columbus.  We  know  now  that  the  reason  for  the  declina- 
tion of  the  needle  is  that  the  north  end  of  it  does  not 
point  toward  the  north  geographical  pole  as  was  at  first 
supposed  but  toward  a  point  in  the  southwestern  part  of 


LINES  OF  EQUAL  MAGNETIC  DECLINATION  IN  THE  UNITED  STATES. 

Boothia  Felix  which  is  called  the  north  magnetic  pole.  The 
south  magnetic  pole  as  recently  determined  is  a  little  to 
the  east  of  Victoria  Land. 

These  magnetic  poles  do  not  remain  in  the  same  place  all 
of  the  time  but  swing  slowly  back  and  forth,  so  that  the 
declination  changes  for  the  same  place.  On  account  of 
this  it  is  necessary  for  surveyors,  who  use  the  compass,  to 
find  out  the  declination  each  year.  The  annual  change  in 
the  United  States  varies  from  0  to  5  seconds.  In  1910 
the  declination  at  Eastport,  Maine,  was  19.4°  west  and  for 
Seattle,  Washington,  23.5°  east.  For  intervening  places 
there  were  intervening  values.  Maps  are  now  made  with 


36 


FIRST   YEAR   SCIENCE 


lines  upon  them  connecting  places  of  equal  declination. 
These  lines  are  called  isogonic  lines. 

18.  Magnetism.  —  Experiment  11.  Having  pushed  a  long  cam- 
bric needle  through  a  small  disk  of  cork  so  that  it  will  float  horizon- 
tally, carefully  place  the  disk  and  needle  upon  the  quiet  surface  of  a 


85 


7o 


105  95  85 

REGION  AROUND  THE  MAGNETIC  POLE. 

large  dish  of  water.  Does  the  needle  assume  any  definite  direction? 
Taking  the  needle  from  the  water  stroke  one  end  of  the  needle  from 
the  cork  out  with  the  north  end  of  a  magnet  and  the  opposite  end 
with  the  south  end  of  a  magnet.  When  the  needle  is  again  floated 
on  the  water  is  it  indifferent  about  the  direction  in  which  it  points  ? 
What  has  caused  the  change,  if  there  is  any  ? 

Experiment  12.  —  Suspend  by  a  string  a  short  bar  magnet  in  a 
sling  made  from  a  bent  piece  of  wire.  Turn  it  around  in  several 
different  directions.  After  each  ^change  allow  it  to  come  to  rest  in 


MAGNETISM  37 

whatever   position  it  will     Does  it  prefer  any  one  position  to  all 
others  ? 

Experiment  13.  —  Suspend  a  bar  magnet  horizontally  in  a  sling 
and  bring  one  of  the  ends  of  another  bar  magnet  toward  it.  What  is 

the  effect?     Reverse  the  ends  of  the  magnet ;  is  there 

any  change  in  the  position  of  the  suspended  magnet? 
Bring  a  large  soft  iron  nail  toward  either  end  of 
the  suspended  magnet.  What  is  the  effect?  Re- 
verse the  ends  of  the  nail.  (Be  careful  that  the  nail 
has  not  become  permanently  affected  by  the  magnet.) 
Is  the  effect  the  same  as  when  the  ends  of  the  magnet 
were  reversed  ? 

Bring  pieces  of  copper,  zinc,  and  other  substances 
toward  the  magnet.  Do  these  affect  it  ?  Notice  that 
the  ends  of  the  bar  magnet  are  marked.  What  can 
you  state  about  the  attraction  or  repulsion  of  similar  ends  of  mag- 
nets ?  Of  opposite  ends  ?  Does  it  make  any  difference  in  its  effect 
on  the  suspended  magnet  toward  which  end  the  nail  is  brought? 
What  substances  do  you  find  attracted  by  the  magnet? 

To  the  end  of  a  small  nail  hanging  by  attraction  to  a  magnet  bring 
another  nail.  How  does  the  first  nail  act  in  respect  to  the  second  ? 

So  much  were  some  of  the  ancients  impressed  with  the 
property  of  loadstones  for  attracting  iron  that  one  of  them 
suggested  building  a  great  arch  of  this  material  in  a  temple 
so  that  the  iron  statue  of  the  goddess  would  remain  sus- 
pended in  the  air  without  resting  upon  any  support. 
There  is  an  old  legend  that  the  iron  coffin  of  Mohamet 
rose  and  remained  near  the  ceiling  of  the  mosque  in  which 
it  was  buried. 

It  was  early  discovered  that  when  pieces  of  steel  were 
rubbed  on  a  loadstone  they  took  on  the  properties  of  the 
loadstone  and  become  magnets.  In  the  experiments  with 
magnets,  it  was  found  that  like  poles  repelled  and  unlike 
poles  attracted,  and  that  iron  or  steel  in  contact  with  a 
magnet  becomes  magnetized.  Iron  and  steel  are  practi- 
cally the  only  substances  attracted  by  a  magnet,  although 


38 


FIRST   YEAR   SCIENCE 


nickel  and  cobalt  and  a  few  other  substances  have  a  little  at- 
traction.    Thus  steel  and  iron  are  always  used  for  magnets. 


Experiment  14.  —  Wind 
twenty  feet  of  No.  20  in- 
sulated copper  wire  around 
the  nail  used  in  Experiment 
13  as  you  would  wind  thread 
on  a  spool.  Attach  one  end 
of  this  wire  to  each  pole  of 
a  dry  cell.  Bring  the  nail 
thus  arranged  toward  a  sus- 
pended magnet.  Reverse 
nail  act  as  it  did  before  it  was 


Fig.   14. 

the  ends  of  the  nail.  Does  the 
placed  within  the  coil  of  wire 
connected  to  the  battery? 
Bring  another  nail  in  con- 
tact with  its  ends.  What 
happens?  What  has  the 
nail  as  arranged  become? 
Disconnect  one  of  the  wires 
from  the  battery  and  try  the 
test  again.  Does  the  .  nail 
act  as  it  did  when  the  bat- 
tery was  connected? 


We  found  that  if  a 
nail  is  placed  in  a  coil 
of  wire  connected  with 
an  electric  battery  it 
becomes  magnetic,  but 
only  as  long  as  the  con- 
nection is  maintained. 
Magnets  of  this  kind 
are  called  electromagnets. 
If  the  nail  had  been  hard 


MAGNETIC  CRANE. 
The  electromagnet  is  lifting  tons  of  scrap 


steel  and  the  battery  exceedingly  strong,  the  steel  would 
have  remained  a  magnet  after  being  taken  out  of  the  coil. 


MAGNETIC  FIELD  OF  FORCE  39 

Magnets  are  at  the  present  time  ordinarily  made  by 
electrical  action  and  not  by  rubbing  on  other  magnets. 
Magnetized  steel  bars  are  called  permanent  magnets. 
Electromagnets  have  become  of  almost  inestimable  use  in 
modern  life.  The  telegraph,  telephone,  magnetic  crane, 
electric  motor,  and  almost  innumerable  other  mechanical 
devices  are  dependent  largely  upon  the  principle  of  elec- 
tromagnetism  for  their  usefulness. 

19.  The  Magnetic  Field  of  Force.  —  Experiment  15.  —  Place  a 
thin  piece  of  cardboard  about  the  size  of  a  sheet  of  writing  paper 
above  a  bar  magnet  and  carefully  sprinkle  iron  filings  over  it.  De- 
scribe the  behavior  of  the  filings.  Sketch  on  a  piece  of  paper  their 
arrangement.  Move  a  small  compass  about  above  the  cardboard 
and  note  the  directions  the  needle  assumes.  How  do  the  actions 
of  the  needle  and  of  the  filings  compare  ? 

Holding  the  small  compass  two  or  three  inches  above  the  magnet 
move  it  parallel  with  the  magnet  from  end  to  end.  Gently  tap  the 
compass  occasionally  so  that  the  needle  will  move  freely.  How  does 
the  needle  act  when  it  is  over  the  ends  of  the  magnet?  How  does 
the  direction  of  the  compass  needle  compare  with  the  direction  of  the 
bar  magnet  ? 

In  the  above  experiment  we  found  that  when  iron 
filings  were  sprinkled  above  the  magnet  they  arranged 
themselves  in  definite  lines.  The  small  compass  needle 
also  arranged  itself  along  these  lines  when  brought  under 
the  influence  of  the  magnet.  There  is,  then,  around  a 
magnet  a  magnetic  field  of  force  which  affects  magnets 
and  magnetic  substances  brought  within  it.  It  is  found 
that  magnetic  intensity,  like  the  intensity  of  sound  and 
light,  varies  inversely  as  the  square  of  the  distance. 

When  the  compass  was  placed  above  the  ends  of  the 
bar  magnet  one  of  the  ends  of  the  needle  was  pulled  down 
toward  the  magnet,  or  it  might  be  said  to  dip  toward  the 
magnet.  When  moved  near  the  middle  of  the  magnet  it 
assumed  a  horizontal  position,  and  when  it  approached  the 


40 


FIRST   TEAR   SCIENCE 


opposite  end  of  the  magnet  the  opposite  end  of  the  needle 
dipped.  This  same  action  is  found  when  a  magnetic 

needle  is  carried  from  north  to 
south  upon  the  earth.  If  a 
needle  is  carefully  balanced  and 
then  magnetized,  it  will  be 
found  no  longer  to  assume  a 
horizontal  position. 

In  the  northern  hemisphere 
the  north  end  will  dip  and  in 
the  southern  hemisphere  the 
south  end.  In  the  northern 
hemisphere  it  is  customary  to 
make  the  south  end  of  the 
needle  a  little  heavier  so  that  it 
will  stay  in  a  horizontal  posi- 
tion. At  the  magnetic  pole 
the  needle  would  stand  verti- 
cal. If  a  needle  is  accurately 
balanced  on  a  horizontal  axis 

and  then  magnetized,  it  will  show  the  angle  of  dip  in  any 
locality.  Such  a  needle  is  called  a  dipping  needle 
(Fig.  15). 

20.  The  Mariner's  Compass.  —  In  the 
ordinary  mariner's  compass  a  magnetic 
needle  is  arranged  so  that  it  will  swing 
freely  in  a  horizontal  plane.  A  circu- 
lar card  is  divided  into  four  equal  parts 
the  dividing  lines  of  which  are  marked 
with  the  cardinal  points  of  the  compass, 
the  intervening  spaces  being  divided 
into  eight  equal  divisions.  The  card  is  attached  to  the 
needle  and  inclosed  in  a  box  called  the  binnacle.  This 
box  is  arranged  so  that  it  will  always  remain  horizontal. 


Fig.  15. 


Fig.   16. 


THEORY  OF  MAGNETISM  41 

A  fixed  line  on  the  binnacle  shows  the  direction  of  the 
keel  of  the  ship.  The  card  being  attached  to  the  needle 
always  has  its  "north"  pointing  toward  the  north.  To 
determine  the  direction  of  the  ship  it  is  only  necessary  to 
notice  on  the  card  in  what  direction  the  keel  line  is  point- 
ing. The  mariner  of  course  must  know  the  declination 
at  the  place  where  he  is  and  make  the  proper  corrections. 
The  different  governments  furnish  tables  and  charts  show- 
ing these  corrections. 

21.   Theory  of  Magnetism.  —  Experiment  16.— Heat  a  No.  20 

knitting  needle  red  hot  and  plunge  it  quickly  into  cold  water.  This 
tempers  the  needle  so  that  it  will  break  readily.  Magnetize  the  needle 
as  was  done  in  Experiment  11.  When  it  has  become  well  magnetized, 
break  it  in  the  middle.  Test  each  half  with  a  suspended  magnet,  as 
was  done  in  Experiment  13.  Is  each  half  a  full  magnet  or  only  half 
a  magnet?  Break  these  halves  again  and  test.  What  effect  does 

breaking  a  magnet  have  upon  the  magnet? 

• 

In  Experiment  16  it  was  found  that  if  a  magnet  is 
broken  in  two,  each  half  is  a  perfect  magnet.  If  these 
halves  are  broken,  each  piece  is  a  perfect  magnet,  and 
so  on  as  long  as  the  division  is  kept  up.  It  is  also  found 
that  if  a  magnet  is  heated  or  suddenly  jarred  or  pounded 
it  loses  its  magnetism.  If  a  magnet  is  filed  into  filings  and 
these  filings  are  put  into  a  glass  tube  the  tube  will  have 
no  magnetic  properties  but  will  act  to  a  magnet  like  an 
ordinary  iron  bar. 

If  now  the  tube  is  held  vertically  and  tapped  several 
times  on  a  strong  magnet,  the  tube  will  be  found  to 
have  acquired  -the  properties  of  a  magnet.  The  tapping 
joggled  the  particles  so  that  they  could  arrange  themselves 
under  the  influence  of  the  magnetic  pole  and  when  they 
became  so  arranged  a  magnet  was  the  result.  If  the  fil- 
ings are  now  poured  out  of  the  tube  and  then  put  back 
again,  there  will  be  no  magnetization. 


CBCB  no 


42  FIRST   YEAR   SCIENCE 

It  was  the  arrangement  of  the  tiny  magnetized  particles 
which  must  have  caused  the  contents  of  the  tube  to  be- 
come magnetic.  It  would  therefore  seem  prob- 
able that  magnetism  must  be  a  property  of  the 
exceedingly  small  particles  or  molecules  of  which 
the  iron  or  steel  as  well  as  all  other  substances 
are  supposed  to  be  composed,, 

It  is  supposed  that  when  a  bar  of 
steel  becomes  magnetized  the  mole- 
cules arrange  themselves  in  definite 
directions,  as  do  the  filings  in  the 
tube.  The  molecules  of  magnetic  sub- 


BBBB 
eeee 
eiie 
eiee 

BiBB 
BiBB 
iiflB 
BBBB 
BBBB 
BBBB 
BBBB 
BBBB 
BBBB 


Fig.  17.      stances   are   supposed   to   be   separate 
little  magnets.     In  the  unmagnetized 
bar  (Fig.  17)  their  poles  point  in  all  directions 
dependent    upon   their   mutual  attraction,  and 
thus  they  neutralize  each  other.     When  the  bar      Fi     18 
becomes  magnetized   the  molecules  tend  to  ar- 
range themselves  so  that  like  poles  lie  in  the  same  direc- 
tion  (Fig.  18).      When  the   magnet  is  heated  or  jarred 
the  molecules  are  moved  out  of  this  alignment  and  the 
magnetism  is  weakened. 

Summary.  —  The  shape  of  the  earth  is  spherical  with 
very  slight  flattening  at  the  poles.  Its  diameter  is  almost 
8000  miles,  more  than  four  times  the  distance  from  New 
York  to  Denver  ;  and  its  circumference  is  nearly  25,000 
miles.  Though  the  irregularities  of  the  earth's  surface 
are  exceedingly  small  in  comparison  with  its  total  area, 
they  are  great  enough  to  have  a  vast  effect  upon  the  life 
of  animals  and  plants. 

The  revolution  of  the  earth  upon  its  axis  causes  day 
and  night,  and  gives  us  our  measurement  of  time  and  our 
points  of  the  compass.  The  movement  of  the  earth 


SUMMARY  43 

around  the  sun,  combined  with  the  inclination  of  the 
earth's  axis,  gives  us  the  seasons.  The  inclination  of  the 
earth's  axis,  combined  with  its  revolution,  and  the  move- 
ment just  mentioned,  gives  us  our  latitude  zones  and 
causes  the  variation  in  the  length  of  our  days  and  nights. 

Direction  east  and  west  on  the  earth  is  measured  by 
meridians  of  longitude  ;  direction  north  and  south  by 
parallels  of  latitude.  There  is  about  seventy  miles  be- 
tween the  different  parallels  and  also  between  the  differ- 
ent meridians  at  the  equator.  There  is  about  the  same 
distance  between  the  parallels  all  the  way  to  the  poles, 
but  as  the  meridians  extend  north  and  south,  the  distance 
between  them  grows  less  and  less  till  they  all  meet  at  the 
poles. 

To  find  the  location  of  a  ship  at  sea  we  use  a  compass, 
a  magnetized  needle  which  points  toward  the  north  mag- 
netic pole,  located  northeast  of  Alaska.  Thus,  the  mag- 
netism of  the  earth  is  of  infinite  value  to  ocean  commerce. 

QUESTIONS 

What  simple  reasons  are  there  for  believing  that  the  earth  is 
round  ? 

What  effects  have  the  irregularities  of  the  earth's  surface  had  on 
life? 

Draw  diagrams  illustrating  what  was  discovered  in  Exp.  8. 

Why  do  we  have  winter  when  the  earth  is  nearest  the  sun  ? 

If  a  man  left  Cairo,  Egypt,  on  June  21  and  traveled  slowly  to  Cape 
Town,  reaching  there  on  Dec.  21,  what  changes  of  seasons  would  he 
experience  ? 

How  is  the  length  of  a  day  determined  ?  If  it  were  noon  Thurs- 
day, Sept.  30,  with  you,  what  would  be  the  day  and  date  at  Yokohama  ? 

Why  is  Standard  Time  particularly  advantageous  in  the  United 
States?  How  much  is  the  difference  between  local  and  standard 
time  at  your  locality  ? 

Suppose  that  a  man  at  the  north  pole  traveled  a  degree  south  and 
then  a  degree  east.  How  far  would  he  travel?  Suppose  he  were  a 


44  FIRST   YEAR   SCIENCE 

degree  north  of  the  equator  arid  traveled  a  degree  south  and  then 
a  degree  east.  How  far  would  he  travel  ?  In  both  cases  he  traveled 
a  degree  of  latitude  and  a  degree  of  longitude.  Do  the  distances 
differ?  If  so,  why? 

If  it  is  12  o'clock  local  time  at  your  home,  what  time  is  it  at  Paris  ? 
At  Honolulu? 

What  practical  advantages  and  applications  of  magnetism  do  you 
know  ? 

Why  is  it  necessary  for  a  mariner  to  know  the  declination  f 


CHAPTER   III 
THE  GIFTS  OP  THE  SUN  TO  THE  EAETH 

22.  Energy.  —  The  capacity  for  doing  work,  for  over- 
coming resistance,  for  causing  change,  is  called  energy. 
If  the  position  of  a  body  or  its  composition  is  such  that  it 
can  exert  force  or  overcome  resistance,  its  energy  is  called 
potential.  If  the  body  is  actually  moving,  it  is  said  to  have 
kinetic  energy. 

When  a  pendulum  bob  is  pulled  aside  and  held  higher 
than  the  lowest  point  of  its  arc,  it  has  potential  energy. 
If  it  is  allowed  to  swing,  it  will  change  this 
potential  energy  into  kinetic.  The  potential 
energy  it  had  when  at  its  highest  point 
is  changed  into  the  same  amount  of  kinetic 
energy  when  it  reaches  the  lowest  point 
in  its  swing. 

When  a  gun  is  loaded  the  powder  has 
^potential  energy  due  to  its  composition,  but  when  it 
explodes  this  is  changed  into  kinetic  energy  which  is 
imparted  to  the  bullet.  The  smallest  possible  piece  of 
nitroglycerine  has  potential  energy  on  account  of  the 
arrangement  of  its  molecules,  and  this  is  capable  of  being 
readily  changed  into  kinetic  energy. 

The  sun  throughout  its  existence  has  been  sending  vast 
quantities  of  energy  to  the  earth.  This  energy  has  been 
mostly  in  the  form  of  heat  and  light.  The  ability  of  the 
earth  to  support  plant  or  animal  life  or  to  furnish  man 
the  power  necessary  to  carry  on  his  industries  is  due  to  the 

45 


46 


FIRST   YEAR   SCIENCE 


energy  furnished  by  the  sun.  Plants  cannot  grow  without 
the  energy  furnished  by  the  sunlight,  and  animals  could  not 
live  were  it  not  for  the  energy  furnished  them  by  the 
plants. 

For  untold  ages  plants  utilized  the  sun's  energy  and 
stored  it  up.  It  was  preserved  in  the  remains  of  plants 
in  the  form  of  coal.  This  coal  is  now  being  burned  to 
furnish  power  to  carry  on  man's  industries.  The  water 
which  the  sun  has  evaporated  and  carried  by  cloud  and 
shower  to  the  mountain  lake  is  stored  there  and  has  po- 
tential energy.  It  is  ready  to  run  down  the  valleys  chang- 
ing its  potential  energy  into  kinetic  and  doing  work.  We 
often  think  that  there  are  many  different  sources  of  energy 
such  as  wood,  coal,  oil,  waterpower  and  others,  but  when 
these  are  traced  back,  their  energy  is  found  to  have  come 
from  one  source,  the  sun. 

Energy  may  readily  be  changed  into  different  forms,  as 
when  the  steam  engine  transforms  the  energy  in  coal  into 


TRANSFORMATION  OF  ENERGY. 


mechanical  energy,  or  when  this  mechanical  energy  is 
changed  by  the  dynamo  into  electrical  energy.  The  most 
careful  investigations  have  shown,  however,  that  although 
its  form  may  change,  energy  can  never  be  destroyed. 


HEAT  AND   LIGHT 


Mechanical  energy  frequently  changes  into  heat,  as  when 
two  surfaces  are  rubbed  together,  but  when  these  two 
kinds  of  energy  are  carefully  measured  there  is  found  to 
be  no  loss.  This  great  truth  has  been  determined  by  a 
vast  amount  of  most  careful  investigation  and  is  called 
the  law  of  conservation  of  energy. 

23.  Heat  and  Light.  —  Every  one  realizes  the  importance 
of  the  heat  and  light  given  to  the  earth  by  the  sun.     If 
plants  or  animals  are  where  light  is  entirely  excluded, 
they  begin  to  sicken  and  die.     If  they  are  placed  where 
it  is  very  cold,  they  freeze  and  die.     Although  the  sun 
gives  both  heat  and  light,  yet  these  two  are 

not  inseparable.  We  feel  the  heat  given  out 
by  boiling  water  but  there  is  no  light,  and 
we  see  the  light  of  the  moon  but  there  is  no 
heat.  We  usually  say  that  we  feel  heat  but 
cannot  see  it  and  see  light  but  cannot  feel  it. 

24.  Heat.  —  Experiment  17.  —  Fit   a   glass   flask 
with  a  one-hole  rubber  stopper  through  which  passes 

a  glass  tube  about  20  cm.  long.  Place  this  on  a  ringstand  so  that 
the  end  of  the  tube  extends  down  into  a  bottle  nearly  filled  with 
n  water.  Gently  heat  the  flask.  The  air  expands 

and   bubbles   rise   in   the   water.     When    the    flask 
cools,  the  air  contracts  and  water  rises  in  the  tube. 

Experiment  18. — Fill  the  flask  used  in  the  last 
experiment  with  colored  water.  See  that  the  end 
of  the  glass  tube  passing  through  the  rubber  stopper 
is  just  even  with  the  bottom  of  the  stopper.  Smear 
the  lower  part  of  the  stopper  with  vaseline  and  in- 
sert it  in  the  flask,  being  careful  that  the  flask  and 

L  a  few  centimeters  of  the  tube  are  filled  with  colored 

P.  j  water  and  that  there  are  no  air  bubbles  in  the 

flask.  Mark,  by  slipping  over  a  rubber  band,  the 

end   of   the  water    column    in   the    tube.      Heat    the    flask.      The 

water  expands.     Why  do  water  heaters  always  have  a  pipe  at  the 

top  leading  to  a  tank? 


48  FIRST   TEAR    SCIENCE 

Experiment  19.  —  Pass  the  ball  of  a  ball-and-ring  apparatus  through 
the  ring.     Notice  how  closely  it  fits.     Heat  the  ball  in  a  Bunsen  flame 
for  several   minutes.     See   if   thq  ball  will   now  go 
through  the  ring.     Explain  why  it  does  not. 

Experiment  20.  —  Heat  a  metal  compound-bar.     It 
bends  over  on  one  side.     The  more  the  bar  is  heated 
the  more  it  bends.     The  two  metals  do  not  expand 
at  the  same  rate.     Why  are  the  ends  of  steam  pipes 
allowed  to  be  free  and  not  attached  firmly  ?     Why  are 
the  ends   of  the  spans  of  long 
iron  bridges  placed  on   rollers?    * 
Fig.  22.          When    iron   tires    are  fitted  to    A^^^*^*'!!!^ 
wheels  they  are  heated  and  then    '  \^ 

placed  on  the  wheels  and  allowed  to  cool.    Why?  pig   23. 

Platinum  is  the  only  substance  that  can  be  used 

to  pass  through  the  glass  in  an  incandescent  lamp.     Other  metals 

do   not  expand  the  same  as  glass  and  when  they   are   fused  with 

it  and  allowed  to  cool  they  break  it. 

When  heat  was  first  studied  it  was  thought  to  be  an 
invisible  fluid  without  weight  which  worked  itself  into 
bodies  and  caused  them  to  expand  in  the  same  way  that 
water  affects  a  sponge  or  a  piece  of  wood.  This  fluid  was 
supposed  to  be  driven  out  by  pounding  or  rubbing. 
Even  the  primitive  savages  knew  that  fire  could  be  ob- 
tained by  rubbing  two  dry  sticks  together. 

About  the  close  of  the  eighteenth  century  an  American, 
Count  Rumford,  who  was  boring  some  cannon  for  the 
Bavarian  government,  showed  that  the  amount  of  heat 
developed  seemed  to  be  entirely  dependent  upon  the 
amount  of  grinding  or  mechanical  energy  expended. 
The  old  theory  of  a  fluid  prevailed  however  until  about 
the  middle  of  the  nineteenth  century,  when  a  great  Eng- 
lish experimenter  by  the  name  of  Joule  showed  conclu- 
sively that  the  amount  of  heat  developed  was  due  entirely 
to  the  amount  of  mechanical  energy  which  apparently  dis- 
appeared into  the  heated  body. 


MEASUREMENT  OF  TEMPERATURE       49 

Every  kind  of  matter  is  now  believed  to  consist  of 
little  particles,  or  molecules,  which  are  constantly  moving 
about  hitting  and  bumping  against  each  other  in  the 
spaces  which  exist  between  them.  The  fact  that  minute 
invisible  particles  may  be  given  off  by  a  substance  is 
readily  shown  by  opening  a  bottle  of  ammonia  or  expos- 
ing a  piece  of  musk  in  a  room.  Soon  in  every  part  of  the 
room  the  presence  of  these  substances  can  be  recognized 
by  the  odor.  Yet  nothing  can  in  any  possible  way  be 
seen  to  have  been  added  to  the  air. 

The  molecules  are  too  small  to  be  seen  by  the  most 
powerful  microscope.  There  are  millions  of  them  in  a 
particle  of  matter  as  big  as  the  head  of  a  pin.  When  a 
substance  is  heated  the  molecules  move  more  rapidly  and 
strike  each  other  harder.  This  causes  the  substance  to 
expand.  Heat  is  denned  as  being  the  motion  of  these 
molecules.  If  a  condition  could  be  reached  where  there 
was  no  molecular  motion,  there  would  be  no  heat.  The 
effect  of  heat  in  causing  expansion  of  gases,  liquids  and 
solids  has  been  shown  in  the  preceding  experiments. 

25.  Measurement  of  Temperature.  —  From  the  experi- 
ments it  has  been  seen  that  gases,  liquids  and  solids  ex- 
pand when  heated  and  contract  when  cooled.  It  has- 
been  found  that  most  substances  expand  uniformly 
through  ordinary  ranges  of  temperature,  so 
that  if  this  expansion  or  contraction  is  meas- 
ured, we  are  able  to  determine  the  change  of 
temperature. 

Experiment   21. —  Slightly   warm   the  bulb  of  an  air 
thermometer  tube  and  place  the  open  end  in  a  beaker 
half  filled  with   inky  water.     Allow  the   bulb   to  cool. 
The  tube  will  become  partly  filled  with  the  water.     When       pj 
the  bulb  has  become  entirely  cooled  mark  the  end  of 
the  water  column  with  a  rubber  band.     Grasp  the  bulb  with   the 
hand,  thus  wanning  the  air  in  it.     The  water  column  will  run  partially 


50  FIRST   YEAR   SCIENCE 

f* 

out  of  the  tube  back  into  the  beaker.  Cool  the  bulb  with  a  piece  of 
ice  or  a  damp  cloth.  The  water  will  come  farther  up  in  the  tube 
than  it  did  when  simply  exposed  to  the  air.  We  have  here  an  ap- 
paratus for  telling  the  relative  temperatures  of  bodies. 

Instruments  arranged  to  show  the  amount  of  the  expan- 
sion or  contraction  of  certain  materials  due  to  changes  in 
their  temperature  are  called  thermometers.  These  may  be 
gas,  liquid  or  metal  thermometers.  There  must  be  some 
uniform  temperatures  between  which  the  expansion  shall 
be  measured  if  we  are  to  have  a  basis  of  comparison. 
These  definite  points  have  been  taken  as  the  freezing  and 
boiling  points  of  water  at  sea  level. 

Experiment  22.  —  Fill  a  four-inch  ignition  tube  with  mercury  and 
insert  a  one-hole  rubber  stopper  having  a  straight  glass  tube  extend- 
ing through  it  and  about  20  cm.  above  it.  It  may 
be  necessary  to  cover  the  stopper  with  vaseline  to 
keep  out  air  bubbles.  When  the  stopper  was  in- 
serted the  mercury  should  have  risen  a  few  centi- 
meters in  the  tube.'  Mark  with  a  rubber  band 
the  end  of  the  mercury  column.  Gently  warm  the 
ignition  tube.  The  mercury  column  rises.  Cool 
the  tube  and  the  column  falls.  We  have  here 
a  crude  thermometer. 

The  substance  whose  expansion  is  most 
commonly  used  to  measure  the  degree  of 
temperature   is   mercury.      This   expands 
Fig.  25.          noticeably  for  an  increase  in  temperature 
and  the  amount  of   its  expansion  can  be 
very    readily    determined.     The    ordinary    thermometer 
consists  of  a  glass  tube  of  uniform  bore  which  has  a  bulb 
at  one  end.     The  bulb   and    part  of   the  tube  are  filled 
with  mercury.     The  remaining  part  of  the  tube  is  empty, 
so  that  the  mercury  can  freely  rise  or  fall.      When  the 
temperature  rises,  the  mercury  expands  and  rises,  when 
the  temperature  falls,  the  mercury  contracts  and  sinks. 


THREE  STATES  OF  MATTER 


51 


There  are  two  kinds  of  thermometer  scales  commonly 
used.  In  one,  the  point  to  which  the  mercury  column 
sinks  when  submerged  in  melting  ice  is  marked 
32°,  and  the  point  to  which  it  rises  at  sea  level 
when  immersed  in  unconfined  steam,  the  boiling 
point,  is  212°.  The  distance  between  the  boil- 
ing and  freezing  points  is  divided  into  180 
equal  parts.  Each  one  of  these  parts  measures 
a  Fahrenheit  degree  of  temperature.  This  is 
the  common  household  thermometer  of  this 
country  and  England. 

Another  kind  of  thermometer  scale,  which 
is  used  almost  exclusively  in  scientific  work 
and  in  those  countries  where  the  metric  system 
of  weights  and  measures  has  been  adopted, 
is  called  the  Centigrade.  In  this  scale,  the 
point  at  which  ice  and  snow  melt  is  marked 
0  and  the  point  at  which  water  boils,  100.  A 
degree  Centigrade  then  is  y^  the  distance  the 
column  expands  when  heated  from  freezing 

to  boiling,  instead  of 
T^  of  this  distance  as 
in  the  Fahrenheit  scale. 
There  are  a  number  of 
different  designs  of 
thermometers.  Some 
are  for  measuring  very 
high,  others  for  measur- 
ing very  low,  tempera- 
tures. Thermometers 
are  also  constructed  so 
as  to  be  self-recording. 

26.   The  Three  States  of  Matter.  —  There  are  three  states 
or  conditions  in  which  substances  exist :  solid,  liquid  and 


THERMOGRAPH. 

This  device  makes  a  continuous  record  of 
the  temperature  for  a  week  at  a  time. 


52  FIRST   YEAR   SCIENCE 

4& 

gas.  Examples  of  these  are :  the  solid  metal  ball,  the 
liquid  water,  the  liquid  metal  mercury,  and  the  gaseous  air. 
These  have  already  been  dealt  with  experimentally.  Al- 
most every  one  knows  that  water  is  a  liquid,  or  a  solid, 
ice,  or  a  gas,  steam,  depending  only  on  the  temperature  to 
which  it  is  subjected.  It  is  not  so  generally  known  that 
the  state  of  all  other  substances  depends  also  upon  their 
temperature. 

Many  substances  are  capable  of  existing  in  all  three 
states.  Iron,  for  instance,  may  be  solid  as  we  ordinarily 
see  it,  or  liquid  as  it  comes  from  a  blast  furnace,  or  a  gas, 
as  it  exists  in  the  tremendously  hot  atmosphere  of  the 
sun.  Substances  usually  expand  in  volume  as  they  change 
from  the  solid  to  the  liquid  state  and  they  always  do  as  they 
change  from  the  liquid  to  the  gaseous.  Ice  is  a  notable 
exception  to  the  general  rule,  since  when  water  freezes  its 
volume  increases.  If  it  were  not  for  this,  ice  would  not 
float.  Metals  that  are  suitable  for  casting  must  have  the 
property  of  expanding  when  cooling  or  at  least  of  shrink- 
ing but  a  trifling  amount.  This  is  a  most  valuable  prop- 
erty of  type  metal  and  cast  iron. 

27.   The  Transference    of    Heat.  —  Experiment  23.  —  Cut  off 

15  cm.  of  No.  10  copper  and  No.  10  iron  wire  and  the  same  length  of 
glass  rod  of  about  the  same  diameter.     Holding  each  of  these  by  one 
end  place  the  opposite  end  in  the  flaine  of  a  Bunsen  burner.     Which 
of  the  three  conducts  the  heat  to  the  hand  first? 

Experiment  24.  —  Fill  a  test  tube  about  f  full  of 
cold  water.  Holding  the  tube  by  the  bottom  carefully 
heat  the  top  part  of  the  water  until  it  boils.  Be  sure 
that  the  flame  does  not  strike  the  tube  above  the  water, 
Fi  27  e^se  the  tube  will  break.  A  little  piece  of  ice  in  the 
bottom  of  the  test  tube  makes  the  action  more  apparent. 
A  bit  of  wire  gauze  or  a  wire  stuffed  into  the  test  tube  will  prevent  the 
ice  from  coming  to  the  surface.  Water  conducts  heat  poorly.  The 
hot  water  does  not  sink.  It  must  be  lighter  than  the  colder  water. 


TRANSFERENCE  OF  HEAT  53 

Without  the  heat  of  the  sun  there  would  be  no  life  upon 
the  earth,  no  flowing  streams,  no  changing  winds,  none  of 
the  restless  energy  which  makes  the  world  as  we  know  it. 
It  is  therefore  essential  to  understand  how  heat  is  trans- 
ferred from  one  place  to  another. 

Through  solid  substances,  such  as  metals,  heat  travels 
quite  readily,  through  others  such  as  glass,  less  rapidly. 
In  Experiment  23,  we  found  that  heat  traveled  along 
some  rods  faster  than  it  did  along  others.  In  no  case, 
however,  was  there  any  indication  that  there  was  a  trans- 
ference of  the  particles  composing  the  rods.  In  the  boiling 
of  the  water  at  the  top  of  the  test  tube,  there  was  no 
indication  that  the  water  particles  moved  to  the  bottom  of 
the  tube.  In  these  cases,  the  heat  is  simply  transferred 
from  molecule  to  molecule. 

This  kind  of  heat  transference  is  called  conduction. 
Conductors  may  be  good  or  bad,  as  was  shown  by  the  dif- 
ferent materials  used  in  the  experiments.  We  use  iron 
for  our  radiators  so  that  the  heat  of  the  steam  may  readily 
be  given  out  to  the  room,  and  we  cover  our  steam  pipes 
with  asbestos  when  we  wish  to  retain  the  heat, 
because  asbestos  is  a  poor  conductor  and  will 
keep  the  heat  in  the  pipes. 


Experiment  25.  —  Hold  a  piece  of  burning  paper 
under  a  bell  jar  held  mouth  downward.  Notice  the 
air  currents  as  indicated  by  the  smoke.  Paper  soaked 
in  a  moderately  strong  solution  of  saltpeter  and  dried 
burns  with  a  very  smoky  flame.  Fig-  28. 

Experiment  26.  —  Fill  a  500  cc.  round-bottomed  flask  half  full  of 
water  and  place  on  a  ring  stand  above  a  Bunsen  burner.  Stir  in  a 
little  sawdust.  Some  of  it  should  fall  to  the  bottom  of  the  flask. 
Gently  heat  the  bottom  of  th'e  flask.  Notice  the  currents. 

When  the  water  was  heated  at  the  bottom  of  the  flask 
and  when  the  burning  paper  was  held  under  the  bell  glass, 


FIRST   YEAR    SCIENCE 


currents  were  seen  to  be  developed.     The  heated  and  ex- 
panded water  and  air  rose.     Here  the  heat  was  transferred 

by  the  upward  move- 
ment of  the  heated 
water  and  air.  This 
method  of  heat  trans- 
ference is  known  as  con- 
vection. The  efficiency 
of  the  hot  water  and  hot 
air  furnaces  which  heat 
our  houses  is  due  to  the 
convectional  transfer- 
ence  Of  heat>  we  shan 

find  later  that  if  it  were 
not  for  convection  there 
would  be  no  winds  or 
ocean  currents. 

If  an  incandescent 
electric  lamp  is  turned 
on  and  the  hand  held 
immediately  below  the 
lamp,  it  will  be  warmed, 
although  the  glass  bulb 
itself,  a  poor  conductor 
of  heat,  remains  cool. 
The  white-hot  filament  is  surrounded  by  an  almost  per- 
fect vacuum.  It  can  set  up  no  convection  currents, 
neither  does  the  cool  glass.  The  sensation  of  heat  can- 
not be  due  to  conduction  because  the  air  which  surrounds 
the  bulb  is  not  in  contact  with  the  filament.  It  is  also  a 
poorer  conductor  than  glass  and  the  glass  itself  does  not 
become  hot  for  some  little  time. 

There  must  therefore  be  another  mode  of  transferring 
heat  be'side  conduction  and  convection.     It  also  appears 


Fig.  29. 


TRANSFERENCE  OF  HEAT 


55 


that  in  this  method  of  transferring,  no  material  substance 

is  necessary,  as  the  hot  filament  is  surrounded  by  an  almost 

perfect  vacuum.     Now  astrono- 
mers tell    us    that    there    is    no 

material   medium    between    our 

atmosphere  and  the  sun  and  that 

the  heat    of    the   sun  travels  to 

us  with  the  tremendous  speed  of 

light,  186,000  miles  per  second, 

and   does   not  warm    the   inter- 
vening space.     The    convection 

and    conduction    processes    are, 

when   compared    to    this,    very 

slow.      Radiation    is    the    name 

given  to  this  method  of  heat 
transference.  If 
heat  did  not 
travel  in  this  way 
the  earth  would 
be  uninhabitable. 
If  a  body, 

heated  to  ordinary  temperatures,  is  sur- 
rounded by  substances  which  do  not  readily 
permit  of  conductional  or  convectional 
heat  transference,  the  heat  is  retained 
within  the  body.  Application  of  this  is 
made  in  the  fireless  cooker  and  the  thermos 
bottle  (Fig.  30).  In  one,  the  hot  substance 
is  surrounded  by  felt,  wood  fiber,  asbestos 
or  similar  nonconducting  substances,  and 
in  the  other  by  glass  and  a  space  from 
which  the  air  has  been  nearly  exhausted. 
Both  of  these  arrangements  prevent  the  transference  of 

heat  from  the  hot  body.     The  cooking  therefore  continues 


HOT  WATER  FURNACE. 
The  hot  water  rises    from 
the  top,  passes  through  the 
radiator     and    returns     as 
colder  water  to  the  bottom. 


Fig.  30. 


56  FIRST  YEAR   SCIENCE 

in  the  fireless  cooker  and  the  liquid  in  the  thermos  bottle 
remains  warm  for  a  long  time  or,  if  cold  when  put  into 
the  bottle,  it  remains  cold,  as  the  heat  from  the  outside 
cannot  reach  it.  Clothing  is  placed  upon  the  body  in 
order  to  prevent  the  body  heat  from  being  conducted  to 
the  surrounding  air. 

28.  The  Measurement  of  Heat.  —  Experiment  27.  —  In  each  of 
two  beakers  or  tin  cups  weigh  out  100  g.  of  watsr.  Carefully  heat 
one  of  the  beakers  until  the  water  when  thoroughly  stirred  shows  a 
temperature  of  90°  C.  Cool  the  other  beaker  till  the  temperature  of 
the  water  is  10°  C.  Pour  the  water  from  one  beaker  into  the  other, 
and  after  thoroughly  stirring  note  the  resulting  temperature.  Use  a 
chemical  thermometer  to  determine  the  temperatures. 

Weigh  out  100  g.  of  fine  No.  10  shot  in  a  tin  cup  and  100  g.  of  water 
in  another.  Place  the  cup  containing  the  shot  in  boiling  water  and 
allow  it  to  remain,  stirring  the  shot  occasionally,  until  its  temperature 
is  90°  C.  Cool  the  water  in  the  other  beaker  until  its  temperature  is 
10°  C.  Determine  the  temperatures  exactly  and  then  pour  the  shot 
into  the  water.  After  thoroughly  stirring  determine  the  temperature 
of  the  mixture.  Which  has  the  highest  temperature,  the  mixture  of 
water  and  water  or  the  mixture  of  shot  and  water? 

Since  heat  plays  such  an  important  part  in  the  activities 
of  the  earth  we  need  to  know  how  to  measure  it.  There 
is  a  great  difference  between  temperature  and  the  amount 
of  heat.  The  amount  of  heat  in  a  spoonful  of  water  at 
100  °  would  be  very  much  less  than  in  a  pailful  of  water 
at  10°.  It  would  require  more  heat  to  raise  a  pond  of 
water  a  small  part  of  a  degree  than  to  raise  a  kettleful 
many  degrees.  That  is  why  large  bodies  of  water,  although 
their  temperatures  never  greatly  change,  exert  so  much 
influence  upon  the  temperature  of  the  surrounding  air. 

Not  only  does  the  amount  of  heat  necessary  to  raise  the 
temperature  of  different  quantities  of  the  same  substance 
vary,  but  the  amount  of  heat  necessary  to  raise  the  tem- 
perature of  equal  quantities  of  different  substances  also 


LIGHT  57 

varies.  If  a  pound  of  water  and  a  pound  of  olive  oil  were 
placed  side  by  side  in  similar  dishes  on  a  stove,  it  would  be 
found  that  the  olive  oil  increases  in  temperature  about 
twice  as  fast  as  the  water,  i.e.  it  takes  about  twice  as 
much  heat  to  raise  water  as  it  does  to  raise  the  same  weight 
of  olive  oil  one  degree.  In  fact,  it  takes  more  heat  to 
raise  a  given  weight  of  water  one  degree  than  it  does  to 
raise  the  same  weight  of  almost  any  other  known  substance. 

In  Experiment  27,  the  resulting  temperature  from  the 
water  mixture  was  much  higher  than  from  the  shot  mix- 
ture. The  shot  has  much  less  capacity  for  heat.  The 
quantity  of  heat  required  to  raise  the  temperature  of  a 
certain  mass  of  a  substance  one  degree  compared  to  the 
quantity  of  heat  required  to  raise  the  same  mass  of  water 
one  degree  is  called  the  specific  heat  of  that  substance. 
The  specific  heat  of  olive  oil  is  .47,  of  shot  .03.  That  is 
it  takes  .47  as  much  heat  to  raise  a  given  mass  of  olive  oil 
and  .03  as  much  heat  to  raise  a  given  mass  of  shot  one 
degree  as  it  does  to  raise  corresponding  masses  of  water 
one  degree.  In  order  to  compare  different  quantities  of  heat, 
physicists  have  taken  as  the  unit  of  measure  the  quantity 
of  heat  required  to  raise  the  temperature 
of  one  gram  of  water  through  one  degree  C. 
This  unit  is  called  a  calorie. 

29.    Light.  —  The    sun    is    not    only    the 
source   of  almost  all  the  heat  of   the  earth 
but  also  of  its  light.      We  have  developed 
artificial     self-luminous     bodies      such      as 
candles,    lamps,    electric     lights,    but    none 
of    these    compares    with    the    light    given 
by    the    sun.       The    stars    also    furnish    a         Flg*  31' 
little    light.      Most    of    the    bodies    that    we    know    are 
dark    and     non-luminous.        Sometimes    some    of    these 
which   have  polished  surfaces    reflect  the    light   from    a 


58  FIRST   YEAR   SCIENCE 

luminous  body  and  thus  appear  themselves  to  be  furnish- 
ing light. 

An  example  of  this  is  often  seen  about  sundown  when 
the  sunlight  is  reflected  from  the  windows  of  a  house,  mak- 
ing them  look  as  if  there  were  a  source  of  light  behind 
them.  Any  dark  body  whose  surface  reflects  light  appears 
itself  to  be  luminous  as  long  as  the  source  of  light  remains, 
but  grows  dark  again  when  the  source  is  removed.  This 
is  the  case  of  the  moon.  At  new  moon,  the  moon  is  so 
situated  with  respect  to  the  sun,  that  light  is  not  reflected 
to  the  earth  and  we  cannot  see  it.  At  full  moon,  half 
of  the  moon's  entire  surface  reflects  the  sunlight,  and 
it  appears  very  bright. 

30.  Direction  of  Light  Movement. — Experiment  28.  —  Point 
the  pinhole  end  of  a  camera  obscura  or  pinhole  camera  (this  consists 

of  two  telescoping  boxes,  the  larger 
having  a  pinhole  at  the  end  and  the 
smaller  a  ground  glass  plate)  at  some 
object  and  move  the  ground  glass  plate 
back  and  forth  until  a*  sharp  image  of 
Pig  32.  the  object  is  formed.  Sketch  on  a  piece 

of    paper  the   object    and  the   image, 

showing  the  direction   in    which  you  think  the  rays  of  light  must 
have  traveled  through  the  pinhole  to  form  the  image. 

A  photographic  camera  is  constructed  in  the  same  way  as  this  little 
camera,  only  a  lens  is  placed  behind  the  pinhole  to  intensify  the 
image,  and  it  is  possible  to  exchange  the  ground  glass  plate  for  a 
photographic  plate. 

There  are  certain  properties  of  light  which  seem  readily 
apparent  from  our  daily  experiences.  We  cannot  see 
objects  in  the'dark,  but  if  a  light  is  brought  into  the  room 
so  that  it  can  shine  upon  them,  they  become  visible.  We 
see  them  because  the  light  is  reflected  to  us  from  them. 
All  objects  except  self-luminous  bodies  are  seen  by  re- 
flected light. 


DIRECTION  OF  LIGHT 


59 


If  a  candle  is  held  in  front  of  a  mirror  and  we  look  into 
the  mirror,  we  see  the  candle  behind  it.  We  know  that 
the  candle  is  not  there  r*rm^^**^ 

but  that  its  light  is  re- 
flected by  the  mirror  in 
such  a  way  as  to  make 
it  appear  to  come  from 
behind  the  mirror.  We 
see  the  candle  by  the 
light  the  mirror  re- 
flects. 

If  we  wish  to  see 
whether  the  edge  of  a 
board  is  straight,  we 
sight  along  it.  If  we 
wish  to  hit  an  object 
with  a  bullet,  we  bring 
the  rifle  barrel  into  our 
line  of  sight.  We  there- 
fore feel  confident  that 
if  light  is  traveling 

through  a  uniform  medium,  such  as  air  usually  is,  it  goes 
in  a  straight  line. 

Experiment  29.  —  Place  a  penny  in  the  center  of  a  five-pint  tin  pan 
resting  on  a  table.  Stand  just  far  enough 
away  so  that  the  outer  edge  of  the  penny  can 
be  seen  over  the  edge  of  the  pan.  Have  some 
one  slowly  fill  the  pan  with  water.  How  is 
the  visibility  of  the  penny  affected? 

Experiment  30.  —  Fill   a  battery  jar  about 
two  thirds  full  of  water.     Place  a  glass  rod  or 
pIG   33^  stick  in  the  jar.     Does  the  rod  appear  straight? 

Pour  two  or  three  inches  of  kerosene  on   the 

top  of  the  water.     What  effect  does  this  have  on  the  appearance  of 
the  rod? 


A  LAKE  MIRROR. 


60  FIRST   YEAR   SCIENCE 

'      '        .  V* 

Experiment  31.  —  Hold  an  ordinary  spectacle  lens  such  as  is  used  by 
an  elderly  person,  or  any  convex  lens,  between  the  sun  and  a  piece  of 
paper.  Vary  the  distances  of  the  lens  from  the  paper.  The  heat  and 
light  rays  from  the  sun  are  bent  so  that  they  converge  to  a  point.  Try 
the  same  experiment  with  a  lens  used  by  a  short-sighted  person,  or  a 
concave  lens.  This  lens  does  not  have  the  same  effect  as  the  convex' 
lens.  The  rays  are  made  to  diverge.  Why  cannot  long-sighted  and 
short-sighted  persons  use  the  same  glasses? 

In  the  experiment  of  the  penny  in  the  dish,  the  water 
in  some  way  bent  the  ray  of  light  and  made  the  penny 
come  into  the  line  of  sight  when  it  could  not  be  seen  before 
the  water  was  there.  This  experiment  shows  that  when 
light  is  passing  from  one  medium  to  another  it  does  not 
always  travel  in  the  same  straight  line.  Certain  media 
offer  more  resistance  to  the  passage  of  light  than  others 
and  are  called  denser  media.  It  is  this  resistance  which 
causes  the  bending  of  the  ray. 

Suppose  that  a  column  of  soldiers  inarching  in  company 
front  are  passing  through  a  corn  field  and  come  obliquely 

upon  a  smooth  open  field.  The 
men  as  they  come  on  to  the 
open  field  are  unincumbered 
by  the  cornstalks  and  will 
move  faster,  and  thus  the  line 
of  march  will  swing  in  toward 
the  edge  of  the  corn  field.  It 
Flg>  34-  can  easily  be  seen  that  the 

bending  of  the  line  would  be  in  the  opposite  direction  if 
the  soldiers  were  marching  from  the  smooth  field  into 
the  corn  field.  If  the  company  front  was  parallel  to 
the  edge  of  the  corn  field,  then  the  men  would  reach  the 
open  field  at  the  same  time  and  there  would  be  no  swing- 
ing of  the  line. 

The  above  illustration  roughly  explains  what  happens 
when  light  passes  from  one  medium  to  another.  Refrac- 


INTENSITY  OF  LIGHT 


61 


tion  is  the  name  given  to  this  bending  of  light  in  passing 
through  different  media  or  through  a  medium  of  changing 
density.  Twilight,  mirage,  the  flattening  of  the  sun's 
disk  at  the  horizon  and  other  appearances  we  shall  find 
later  are  due  to  this  property  of  light. 

31.   The  Intensity  of  Light.  —  Experiment  32.  —  Take  two  square 
pieces  of  paraffin  about  an  inch  thick,  or  better  two  squares  of  para- 
wax,  and  place  back  to  back  with  a  piece  of  cardboard  or  tinfoil  be- 
tween them.     When  a  light 
is  placed  on  either  side  of 
this      apparatus     the     wax 
toward  the  light  will  be  il- 
luminated, but  not  that  on 
the  other  side   of  the   card- 
board.    If  lights  are  placed 
on   each  side,  it  is  easy   to 


light. 


Fig.  35. 
In  this  way  the  strengths  of 


see  when  both  pieces  of  wax 
are  equally   illuminated,   or 
receive  the   same  amount  of 
lights  can  be  compared. 

Place  a  candle  about  25  cm.  in  front  of  one  side  of  this  apparatus, 
and  4  candles,  placed  close  together  on  a  piece  of  cardboard  so  that 
they  can  be  readily  moved,  about  90  cm.  away  on  the  other  side. 
Move  these  candles  back  and  forth  till  a  position  is  found  where  both 
pieces  of  wax  are  illuminated  alike.  Measure  the  distance  of  the  four 
candles  from  the  wax.  How  many  times  as  far  away  are  they  than 
the  one  candle? 

The  brightness  of  the  sun's  light  is  so  great  that  even  an 
arc  light  placed  in  direct  sunlight  appears  like  a  dark  spot. 
So  great,  however,  is  the  sun's  distance  that  the  earth  re- 
ceives only  a  minute  portion,  less  than  one  two-billionth  of 
the  light  and  heat  it  gives  out.  It  is  impossible  to  express 
the  greatness  of  this  light  in  ordinary  terms.  The  stand- 
ard measure  for  intensities  of  light  is  the  candle  power. 
This  is  the  light  given  out  by  a  standard  candle,  which  is 
practically  our  ordinary  No.  12  paraffin  candle.  The 


62 


FIBST   YEAR   SCIENCE 


electric 


light   is   sixteen    candle 


ordinary  incandescent 
power. 

No  comprehensible  figures  will  express  the  intensity  of 
the  sun,  using  the  candle  power  as  a  measure.  The  inten- 
sity of  light,  like  that  of  heat  and  electricity,  and  all  forms 
of  energy  which  spread  out  uniformly  from  their  point  of 
origin,  varies  inversely  as  the  square  of  the  distance  from 
the  source.  This  rapid  decrease  in  the  brightness  of  light 


Fig.  36. 

as  the  distance  increases  is  the  reason  why  so  small  a 
change  in  the  distance  of  a  lamp  makes  so  great  a  differ- 
ence in  the  ease  with  which  we  can  read  a  book.  If  we 
make  the  distance  to  the  lamp  half  as  great,  we  increase 
the  amount  of  light  on  the  book  four  times  (Fig.  36). 

32,  Reflection  of  Heat  and  Light.  —  Experiment  33.  —  In  a 
darkened  room  reflect  by  means  of  a  mirror,  a  ray  of  light  from  a 
small  hole  in  the  curtain,  or  from  some  artificial  source  of  light,  on  to 
a  plane  mirror  lying  flat  upon  a  table.  If  there  is  not  sufficient  dust 
in  the  air  to  make  the  paths  of  the  ra}7s  apparent,  strike  two  black- 
board erasers  together  near  the  mirror.  Hold  a  pencil  vertical  to  the 
mirror  at  the  point  where  the  rays  strike  it.  Compare  with  each 
other  the  angle  formed  by  each  ray  with  the  pencil.  Raise  the  edge 
of  the  mirror,  and  notice  the  effect  on  the  reflected  ray.  Place  the 
pencil  at  right  angles  to  this  new  position  of  the  mirror,  and  compare 
the  angles  in  each  case.  How  do  the  sizes  of  the  angles  on  either  side 
of  the  pencil  compare  ? 

It  has  already  been  stated  that  the  moon  shines  b}r  re- 
flected light.  It  is  a  matter  of  common  observation  that 


REFLECTION   OF  HEAT  AND  LIGHT 


63 


objects  on  the  earth  reflect  both  heat  and  light.  In  the 
summer,  the  walls  of  the  houses  and  the  pavements  of  the 
streets  sometimes  reflect  the  heat  to  such  an  extent  that  it 
becomes  almost  unbearable.  In  countries  where  the  sun 
shines  brightly  nearly  all  of  the  time,  as  in  the  Desert  of 
Sahara,  reflectors  have 
been  so  arranged  .as  to 
reflect  the  heat  of  the 
sun  on  to  boilers  and  to 
run  steam  engines. 

The  smooth  surfaces 
of  houses  often  reflect 
so  much  of  the  light 
falling  upon  them  that 
the  glare  is  thrown  into 
the  windows  of  sur- 
rounding houses  into 
which  the  sun  itself 
cannot  shine.  If  one 
stands  in  the  right  posi- 
tion, the  reflection  of 
trees  and  other  objects 
can  be  seen  in  a  smooth 
lake.  But  the  reflec- 
tion cannot  be  seen  if  the  position  of  the  spectator  is 
much  changed.  The  reflected  ray  must  therefore  main- 
tain a  certain  relation  to  the  ray  that  strikes  the  surface 
from  the  object. 

In  Experiment  33,  when  the  pencil  was  held  perpen- 
dicular to  the  mirror  at  the  point  where  the  rays  touched  the 
mirror,  it  was  seen  that  both  the  ray  from  the  window  and 
the  reflected  ray  made  about  the  same  angle  with  it.  These 
two  angles  are  respectively  called  the  angle  of  incidence  and 
the  angle  of  reflection.  By  most  careful  experimentation 


A  REFLECTION  ENGINE. 

This  engine  used  the  rays  of  the  sun  in- 
stead of  coal  to  heat  its  boiler. 


64 


FIRST  YEAE  SCIENCE 


.  Fig.  37. 


it  has  been  found  that  the  angles  between  each  of  these  two 
rays,  and  the  line  drawn  perpendicularly  to  the  reflecting 

surface  are  always  equal,  or  in 
other  words  the  angle  of  reflec- 
tion is  always  equal  to  the  angle 
of  incidence.  This  explains 
why,  if  you  are  standing  in  a 
room  beyond  one  side  of  a 
mirror,  you  can  see  in  the  mirror*  only  the  opposite  side 
of  the  room. 

33.  The  Speed  of  Light  —  In  the  latter  part  of  the  seven- 
teenth century  a  Danish  astronomer  by  the  name  of 
Roemer,  after  carefully  watching  the  brightest  of  Jupi- 
ter's satellites  or  moons  as  it  re- 
volved around  the  planet,  noticed 
that  the  time  of  occurrence  of 
its  eclipses  or  passages  behind 
the  planet  showed  a  peculiar 
variation.  He  accurately  deter- 
mined the  interval  between  two 
eclipses  or  the  time  it  took  for  a 
complete  revolution  of  the  satellite  around  the  planet. 

Using  this  interval  he  computed  the  time  at  which 
other  eclipses  should  take  place  and  found  that  as  the 
earth  in  its  revolution  around  the  sun  moved  away  from 
Jupiter  the  eclipses  appeared  to  take  place  more  and  more 
behind  time.  Determining  the  exact  time  at  which  an 
eclipse  took  place  when  the  earth  was  nearest  to  Jupiter, 
and  computing  the  time  an  eclipse  should  take  place  six 
months  later  when  the  earth  was  farthest  from  Jupiter, 
he  found  that  the  actual  time  of  the  eclipse  was  22  min- 
utes behind  the  computed  time.  This  slowness  he  said 
must  be  due  to  the  time  required  by  the  light  in  crossing 
the  earth's  orbit. 


Fig.  38. 


•    SOUND  65 

Many  determinations  of  this  kind  have  been  made  since 
those  of  Roemer,  and  it  has  been  found  that  he  was  some- 
what in  error,  as  the  time  required  by  light  in  traveling 
across  the  earth's  orbit  is  about  16  minutes  and  40  seconds, 
or  1000  seconds.  Since  the  diameter  of  the  earth's  orbit 
is  about  186,000,000  miles  the  speed  of  light  must  be 
about  186,000  miles  per  second.  Determinations  of  the 
speed  of  light  have  been  made  in  several  other  ways  with 
almost  like  results. 

34.  Theories  Concerning  Light.  —  Although  it  is  very  easy 
to  perceive  light  and  to  examine  many  of  its  properties, 
yet  to  determine  just  what  it  is  that  produces  the  light 
sensation  has  been  found  vastly  difficult.     Sir  Isaac  New- 
ton thought  that  light  consisted  of  streams  of  very  mi- 
nute particles,  or  corpuscles,  thrown  off  by  the  luminous 
body.     Since  about  1800,  it  has  been  considered  a  form 
of  wave  motion  which  is  transmitted  through  the  ether 
which  fills  all  space. 

35.  Sound.  —  Experiment  34.  —  Arrange  a  large  wide- 
mouthed  bottle  with  a  small  bell  suspended  in  it  from 
the  stopper  and  a  delivery  tube  extending  through  the 
stopper.     Attach    the   delivery  tube   by   a    thick- walled 
rubber  tube  to  an  air  pump  and  exhaust  the  air  from 
the  bottle.     Shake   the  bottle   so  that  "the  bell  can  be 
seen  to  ring  but  does  not  strike  the  sides  of  the  bottle. 

Can  the  sound  be  heard  distinctly  ?  Fig.  39. 

Although  sound  is  not  related  to  the  sun's  energy  it 
seems  best  for  certain  reasons  to  consider  it  briefly  in  this 
place.  In  Experiment  34,  it  was  found  that  if  the  air 
was  exhausted  and  the  bell  did  not  touch  the  sides  of 
the  bottle,  almost  no  sound  was  heard  when  the  clapper 
of  the  bell  showed  that  the  bell  was  ringing.  This  shows 
that  the  sounds  we  usually  hear  are  transmitted  in  some 
way  by  the  aid  of  the  air. 


66  FIRST  YEAR   SCIENCE 

'  '  .  v«* 

Sound  has  been  found  to  be  a  wave  motion  in  a  material 
medium.  If  a  scratch  is  made  on  the  end  of  a  long  log, 
it  can  be  heard  if  the  ear  is  placed  at  the  other  end  of 
the  log,  when  it  cannot  be  heard  if  the  ear  is  away  from 
the  log.  In  this  case  the  medium  is 
the  wood. 

If  a  stone  is  dropped  into  a  quiet 
pond,  the  rippling  waves  developed 
will  extend  often  to  the  farthest  shore 
of  the  pond,  but  a  chip  floating  near 
where  the  stone  fell  will  not  be  moved 
from  its  position  except  up  and  down. 
Fig.  40.  Thus  the  waves  traveled  outward  from 

the  point  of  origin,  but  there  was  no  outward  movement 
of  the  water.  If  a  long  rope,  attached  at  one  end  and 
held  in  a  horizontal  position,  is  suddenly  struck  with  a 
stick,  a  wave  motion  will  travel  along  the  rope  from  end 
to  end,  but  the  particles  of  the  rope  will  simply  move  up 
and  down.  It  is  in  a  similar  way  to  this  that  the  sound 
waves  travel,  but  the  particles  which  transmit  the  sound 
only  move  back  and  forth  through  small  distances. 

Summary.  —  All  energy  upon  the  earth  is  due  to  the 
sun.  There  are  two  kinds  of  energy,  kinetic  and  poten- 
tial. Energy  may  be  changed  in  countless  ways  but  it 
cannot  be  destroyed. 

Heat  is  a  form  of  molecular  energy.  Heat  is  shown  in 
changes  in  temperature  and  these  are  measured  by  ther- 
mometers, of  which  the  Fahrenheit  and  the  Centigrade  are 
the  commonest.  Heat  affects  the  state  of  matter:  the 
same  substance  may  be  solid,  liquid  or  gaseous,  depending 
on  the  amount  of  heat  to  which  it  has  been  subjected. 
This  is  shown  in  ice,  water  and  steam.  Heat  is  trans- 
ferred by  conduction,  convection  and  radiation.  The 


SUMMARY  67 

unit   for   measuring   the    amount   of   heat   is   called   the 
calorie. 

Light  moves  at  the  almost  unbelievable  rate  of  nearly 
two  hundred  thousand  miles  a  second.  It  goes  straight 
except  when  passing  at  an  angle  through  media  of  different 
densities.  It  is  then  refracted.  Its  intensity  varies  in- 
versely as  the  square  of  the  distance  from  the  source. 
When  light  is  reflected  from  any  smooth  surface  like  a 
mirror,  the  angle  of  reflection  is  equal  to  the  angle  of 
incidence. 

Sound,  like  light,  is  a  wave  motion.  But  sound  waves 
can  travel  through  substances  that  shut  out  all  light,  and  on 
the  other  hand  light  waves  can  travel  through  a  vacuum 
that  shuts  out  all  sound.  So  the  intensity  of  light  or 
sound  depends  largely  upon  the  medium  through  which  it 
is  conveyed. 

QUESTIONS 

Why  would  it  be  true  to  say  that  all  artificial  light  is  the  sun's 
light? 

Germany  uses  the  Centigrade  thermometer  scale.  If  the  tempera- 
ture of  Berlin  is  reported  as  20°  C.  what  would  the  corresponding 
temperature  be  in  the  thermometer  scale  generally  used  in  the 
United  States  ? 

Why  are  iron  and  type  metal  better  suited  for  casting  than  copper 
and  zinc  ? 

In  what  three  ways  is  heat  transferred? 

Describe  how  you  could  prepare  from  the  ordinary  materials  you 
have  at  hand  a  crude,  inexpensive  fireless  cooker. 

Ponds  near  the  Great  Lakes  freeze  entirely  over.  Why  do  not  the 
Great  Lakes  freeze? 

What  experiences  have  you  ever  had  illustrating  refraction  ? 

If  a  boy  is  reading  two  feet  from  a  light  and  moves  to  a  distance  of 
eight  feet,  how  much  ought  the  light  to  be  increased  to  enable  him  to 
read  with  the  same  ease? 

When  the  sun  is  shining  brightly,  why  is  it  hotter  standing  on  a 
smooth  pavement  than  on  the  grass? 

How  long  does  it  take  light  to  come  from  the  sun  to  the  earth  ? 


CHAPTER  IV 


THE  EARTH'S  CRUST 

36.  Land  and  Water  Areas.  —  The  surface  of  the  earth  has 
an  area  of  about  197,000,000  square  miles,  about  28  per 
cent  of  which  is  land.     Such  areas  are  too  vast  for  us  to  con- 
ceive, but  it  may  help  us  toward  a  conception  to  know  that 
the  area  of  the  United  States,  exclusive  of  Alaska  arid  islands 
belonging  lo  it,  is  about  ^  of  the  land  area  of  the  earth. 

It  is  possible  to  divide  the  surface  of  the  globe  into  two 
hemispheres,  one  of  which  contains  the  larger  part  of  its 
land  and  the  other  the  larger  part  of  its  water  surface. 

This  bunching  of  the 
land  has  brought  the 
people  of  the  earth 
near  together  and  has 
greatly  facilitated 
their  intercourse,  es- 
pecially since  land 

LAND  AND  WATER  HEMISPHERES.  transportation  has  be- 

come  so  easy.  Under 
the  climatic  condi- 
tions which  exist,  it  is  very  advantageous  also  for  the  in- 
habitants of  the  earth  that  the  greater  part  of  the  polar 
lands  are  around  the  north  pole  instead  of  the  south.  The 
fact  that  the  land  masses  have  irregular  outlines  and  are 
separated  by  water  areas  instead  of  being  in  one  continuous 
extent  is  also,  as  we  shall  see,  of  benefit  to  the  earth's  in- 
habitants. 

37.  Interchange  of  Land  and  Water  Areas.  —  It  has  been 
found  from  numerous  observations  that  the  land  and  sea 

68 


Notice  that  London  is  about  at  the  center  of 
the  land  hemisphere. 


LAND  AND    WATER  AREAS 


69 


do  not  always  maintain  the  same  relation  to  each  other. 
Areas  which  at  one  time  were  land  have  since  become  sea 
and  those  which  were  once  sea  are  now  land.  Sea  shells 
are  found  imbedded  in  the  rocks  far  from  the  sea  and 
old  river  valleys  are  found  by  soundings  under  the  sea 
at  considerable  distances  from  the  present  mouths  of  the 
rivers.  What  were  once  sea  beaches  are  now  found  hun- 
dreds of  feet  above  the  sea. 

From  some  such  marks  on  the  coast  of  northern  Sweden 
it  appears  that  the  coast  has  risen  about  seven  feet  during 
the  last  150  years.  The  Netherlands  are  sinking.  Ob- 
servations along  the  coast  of  Massachusetts  give  reason  to 
believe  that  it  is  sinking  very  slowly.  Indications  of  the 
movement  of  the  land  in  respect  to  the  sea  are  found  in 
all  parts  of  the  world. 


OLD  SEA  BEACHES,  SAN  PEDRO. 
Three  old  beaches  can  be  distinctly  seen  on  the  promontory. 

Old  sea  beaches  are  found  rising  one  above  the  other 
along  the  entire  slope  of  a  high  hill  at  San  Pedro,  near  the 


TO 


FIRST   TEAE   SCIENCE 


port  of  Los  Angeles,  California.  Suess,  the  great  Austrian 
geologist,  thinks  that  the  great  changes  of  level  between  the 
sea  and  the  land  are  due  to  a  rising  and  falling  of  the  sea 
and  not  a  rising  and  sinking  of  the  land.  However  this 
may  be,  there  have  been  marked  changes  of  level  between 
the  two  and  the  boundary  between  sea  and  land  has  been 
a  varying  line.  Sea  and  land  areas  have  frequently  inter- 
changed, although  deep  sea  bottoms  were  probably  never 
dry  land. 

38.   Characteristics  of  Land  Surfaces.  —  The  surface  of  the 
land  differs  from  that  of  the  sea  in  being  at  least  com- 


OLD  ROCK  BEACH,  IMPERIAL  VALLEY,  CALIFORNIA. 
Formerly  part  of  the  coast  line  of  the  Gulf  of  California. 

paratively  immovable.  It  is  rough  and  irregular,  and  is 
composed  of  many  different  kinds  of  rocks  and  soils.  For 
the  larger  part  of  its  area  it  rises  above  the  level  of  the  sea, 


CHARACTERISTICS   OF  WATER  71 

but  in  a  few  places  it  sinks  below,  as  in  the  Salton  Sea, 
a  part  of  Imperial  Valley,  California,  and  near  the  Dead 
Sea.  Its  surface  is  eroded  by  wind  and  water  and  is  thus 
constantly  but  slowly  changing  its  features.  Travel  upon 
the  land,  over  most  of  the  earth's  surface,  is  difficult  be- 
cause of  the  irregularities. 


SALT  WORKS  ON  THE  SHORE  OP  THE  SALTON  SEA. 

In  1905  the  Colorado  River  broke  through  into  this  depression,  which  is  below 
sea  level,  and  completely  covered  the  salt  works  seen  in  the  picture. 

Surface  conditions  also  vary  greatly  over  small  areas. 
Great  temperature  changes  occur  on  the  land  between  day 
and  night  and  between  summer  and  winter.  Land  animals 
must  exert  considerable  muscular  force  to  move  about, 
yet  they  must  all  move  to  get  their  food.  They  must 
therefore  be  highly  organized  to  maintain  themselves  upon 
the  land.  Water  animals  are  not  subjected  to  the  same 
difficult  conditions.  In  fact,  the  conditions  of  life  on  sea 
and  land  surfaces  are  entirely  different. 

39.  Characteristics  of  Water.  —  Experiment  36.  —  Place  in  a  dish 
of  fresh  water  a  density  hydrometer,  or  stick  loaded  with  lead  at  one 
end,  so  that  it  will  float  upright.  Mark  with  a  rubber  band  the  point 


72 


FIRST   YEAR   SCIENCE 


to  which  the  hydrometer  sinks  in  the  water.     In  a  dish  sufficiently 

deep  for  the  hydrometer  to  float  dissolve  a  considerable  quantity  of 
salt  in  water.  After  the  salt  has  ^become  thoroughly 
dissolved  taste  the  water  at  the  top  and  then  after  pour- 
ing off  the  larger  part  of  the  water  taste  that  at  the 
bottom  of  the  dish.  The  salt  is  present  in  all  the  water 
but  the  appearance  of  the  water  has  not  changed. 

Now  place  the  hydrometer  in  the  water  containing 
the  dissolved  salt.  It  does  not  sink  to  the  same  depth 
that  it  did  in  the  fresh  water.  What  can  be  said  about 
the  buoyancy  of  water  which  contains  substances  in 
solution?  Does  a  fish  need  to  exert  muscular  force  to 
float  in  water?  Since  water  contains  many  substances  in 

solution,  it  is  possible  for  a  water  animal  that  does  not  move  to 

be  continually  supplied  with  food. 


Fig.  41, 


Experiment  36.  —  (Teacher's  experiment).  Place  a  small  handful  of 
zinc  scraps  in  a  strong  wide-mouthed  bottle.  Fit  the  bottle  with  a 
two-hole  rubber  stopper  having  a  thistle  tube  extending  through  one 
hole  and  a  bent  delivery  tube  through  the  other.  The  thistle  tube 
should  reach  nearly  to  the  bottom  of  the  bottle.  Connect  the  delivery 
tube  with  the  shelf  of  a  pneumatic  trough  by  a  rubber  tube. 
Have  several  inverted  8  oz.  wide-mouthed  bottles  filled  with  water 
on  the  shelf  of  the  trough.  Pour  enough  water  through  the  thistle 
tube  to  partly  cover  the  zinc  and  then  pour  on  commercial  hydro- 
chloric acid  or  sulphuric  acid  diluted  1  to  10. 

Chemical  action  will  take 
place  between  the  zinc  and 
the  acid  and  hydrogen  will 
be  freed.  Allow  the  gas  to 
escape  for  several  minutes, 
as  this  is  largely  the  air 
which  was  in  the  bottle. 
Collect  several  bottles  full 
of  the  hydrogen.  Keep  the 
bottles  inverted.  Examine 
the  hydrogen  in  one  of  the  Pig>  42. 

bottles.    Has  it  color  or  odor  ? 

Holding  the  mouth  downward  thrust  a  lighted  splinter  into  an- 
other bottle.  The  splinter  does  not  continue  to  burn  in  this  gas 
but  the  gas  itself  burns.  Place  another  bottle  mouth  up  on  the 


CHARACTERISTICS  OF  WATER  73 

table  and  allow  it  to  stand  for  several  minutes.     Insert  a  lighted 
splinter.     Why  is  not  the  hydrogen  still  present? 

Draw  out  a  glass  tube  so  that  the  bore  will  be  about  as  large  as 
the  point  of  a  pencil  and  insert  it  in  the  rubber  delivery  tube.  Pour 
more  acid  into  the  bottle  and  after  this  has  been  working  for  several 
minutes  touch  a  lighted  match  to  the  glass  tip  of  the  rubber  delivery 
tube.  A  jet  of  burning  hydrogen  will  be  formed.  Hold  a  cold  dry 
beaker  over  this  burning  jet.  Water  drops  will  collect  in  the  beaker. 
The  hydrogen  is  combining  with  the  oxygen  of  the  air  and  water  is 
being  formed. 

Pure  water  is  a  chemical  compound  of  two  gases,  hy- 
drogen and  oxygen.  The  oxygen  we  have  always  been 
familiar  with,  as  it  makes  up  about  one  fifth  of  the  air  by 
which  we  are  surrounded.  The  hydrogen  was  prepared 
in  the  previous  experiment.  It  is  a  colorless  transparent 
gas,  the  lightest  of  all  substances,  and  must  be  handled 
carefully.  If  it  is  mixed  with  oxygen  or  air  and  the 
mixture  ignited,  it  explodes  with  much  violence,  forming 
water. 

Experiment  37.  —  Fill  a  small  beaker  with  fresh  water.  Heat  it 
slowly.  Bubbles  collect  on  the  bottom  and  sides.  When  the  water 
becomes  cold  these  bubbles  do  not  disappear.  If  they  were  steam, 
they  would  change  back  to  water.  What  are  they?  Wliere  did  they 
come  from  ?  Does  water  contain  dissolved  air  ?  How  can  water 
animals  that  do  not  come  to  the  surface  obtain  the  air  they  need? 

Experiment  38.  —  Put  a  piece  of  ice  in  water.  What  part  of  its 
volume  sinks  below  the  surface  of  the  water?  Is  it  heavier  or  lighter 
than  water?  From  Experiment  24  do  you  conclude  that  cold  water 
is  heavier  or  lighter  than  warm  water  ? 

The  water  that  we  usually  see  has  air  and  other  sub- 
stances dissolved  in  it,  for  water  is  the  greatest  solvent 
known.  Another  property  of  water  which  is  very  im- 
portant is  its  practical  incompressibility.  No  matter  how 
much  pressure  may  be  put  upon  water  its  volume  is  little 
decreased  and  its  density  little  changed.  So  it  happens 


74 


FIRST   YEAR   SCIENCE 


that  substances  which  readily  sink  in  the  upper  part  of 
the  sea  sink  to  the  bottom  no  matter  how  deep  the  water 
may  be,  as  the  bottom  is  so  little  denser  fchan  the  top. 

The  substances  that  are  dissolved  in  water  mix  thor- 
oughly together.  In  isolated  bodies  of  water  there  are 
often  great  differences  in  the  amount  and  kinds  of  dis- 
solved materials,  but  over  the  whole  ocean  from  top  to 
bottom  the  composition  of  the  water  is  practically  uniform. 
From  previous  experiments  we  have  learned  some  of 
the  chief  physical  properties  of  water,  so  perhaps  we  can 
understand  the  different  effects  that  water  and  land  have 
had  upon  the  development  and  activities  of  living  things 
upon  the  globe.  Some  water  animals  move  about  easily 

to  get  their  food,  but 
others  have  it  brought 
to  them  in  solution  and 
so  obtain  it  without 
muscular  effort.  The 
air  that  they  breathe 
is  in  solution  and  they 
cannot  as  easily  obtain 
a  large  quantity  of  it  as 
can  the  land  animals. 
Since  the  energy  of  all 
animals  depends  upon 
the  amount  of  oxygen  they  use  in  their  bodies,  the  water 
animals  are  generally  less  energetic  than  the  land  ani- 
mals. Since  they  also  have  such  an  easy  time  in  moving 
or  floating  about  to  get  the  things  they  need  they  have 
not  developed  as  high  organisms  as  the  land  animals. 

Water  is  readily  moved  by  the  winds  and  becomes  a 
means  of  cutting  dow^n  the  land  and  carrying  away  its 
material.  When  heated  by  the  sun  or  any  other  source 
of  heat  it  evaporates  and,  rising  into  the  air,  floats  away 


CORALS. 

These    are    fixed    animals   whose    food 
brought  to  them  in  solution  by  the 
ocean  currents. 


MATERIALS   COMPOSING   THE  LAND  75 

to  be  condensed  and  to  fall  as  rain  or  snow.  It  takes  a  great 
deal  of  heat  to  evaporate  water  and  all  this  heat  is  given 
off  when  it  condenses.  Water  seeks  the  lowest  place  it  can 
find,  giving  out  energy  as  it  flows.  In  fact,  the  earth  has 
been  likened  by  some  writers  to  a  water  engine,  since 
water  has  played  such  an  important  part  in  its  history. 

Another  property  of  water  which  is  of  great  importance 
is  its  power  to  take  up  heat.  This  was  shown  in  Experi- 
ment 27.  When  it  cools,  it  gives  out  the  heat  it  took 
up  when  its  temperature  was  raised.  It  is  for  this  reason 
that  hot  water  bags  are  used  to  keep  people  warm,  and 
that  farmers  sometimes  in  winter,  when  they  fear  that 
their  cellars  will  freeze,  carry  down  tubs  of  water  to  keep 
their  cellars  above  the  freezing  point.  This  is  why  orange 
groves  are  often  irrigated  just  before  there  is  danger  of  a 
heavy  frost. 

A  pound  of  water  in  cooling  one  degree  gives  out  about 
as  much  heat  as  a  pound  of  iron  in  cooling  9  degrees. 
This  capacity  for  holding  heat  makes  bodies  of  water 
warm  up  slowly  in  the  summer  and  cool  off  slowly  as 
winter  approaches.  As  they  cool  they  give  back  to  the 
air  the  heat  they  have  taken  up.  During  the  early  part 
of  the  summer  the  air  above  them  is  kept  cool  and  in  the 
fall  it  is  warmed.  This  property  of  water  will  be  found 
later  to  be  of  great  importance. 

40.  Materials  Composing  the  Land.  —  Experiment  39.— Ob- 
tain specimens  of  the  igneous  rocks,  lava,  obsidian,  basalt,  granite  ; 
of  the  sedimentary  rocks,  sandstone,  fossiliferous  limestone,  conglom- 
erate, peat ;  of  the  metamorphic  rocks,  shale,  schist,  marble,  anthra- 
cite coal.  Examine  these  carefully  with  the  eye  and  with  the  lens, 
noting  whether  they  have  a  uniform  composition  or  are  made  up  of 
different  particles.  Are  the  particles  composing  the  rocks  crystalline  ? 
Are  they  scattered  irregularly  or  arranged  in  layers  ?  Test  with  a  file 
or  knife-blade  the  hardness  of  the  rock  as  a  whole  and  of  its  differ- 
ent constituents.  Try  a  drop  of  hydrochloric  acid  on  the  different 


76 


FIRST   YEAR   SCIENCE 


rocks  to  see  whether  they  are  affected  by  it.     Describe  in  a  general 
way  the  characteristics  of  each  specimen. 


The  composition  of  differ- 
ent land  areas  varies  greatly. 
Many  different  kinds  of  rocks 
are  often  found  crowded  to- 
gether, or  it  may  happen  that 
the  same  kind  of  rock  covers 
a  large  area.  There  is  no  uni- 
formity. The  soil  on  top  of 
the  rock  is  also  variable.  In 
some  places  it  contains  the 
minerals  which  are  in  the  rock  below  and  in  other  places 
its  composition  is  not  at  all  dependent  upon  the  bed  rock. 


GRANITE. 

Igneous  rock  formed  deep  below 
the  surface  of  the  earth. 


< 


FOSSIL-BEARING  LIMESTONE. 
A  sedimentary  rock  formed  from  sea  shells. 

The  great  variety  of  rocks  of  which   the  crust  of  the 
earth   is   composed    has   been   divided   into   three   great 


MATERIALS   COMPOSING   THE  LAND 


11 


groups  in  accordance  with  the  manner  in  which  they  were 
formed.  These  groups  are  igneous,  sedimentary  and  meta- 
morphic. 

The  igneous  rocks  are  those  which  have  solidified  from 
a  melted  condition.  They  may  have  solidified  deep  down 
within  the  crust,  or  on  the  surface,  or  somewhere  between 
the  depths  and  the  surface.  If  these  rocks  cooled  slowly, 


CONGLOMERATE. 
A  sedimentary  rock  formed  from  old  gravel  beds. 

they  will  have  a  crystalline  structure,  as  in  granite,  and  if 
very  rapidly,  a  glassy  structure,  as  in  obsidian.  Their 
structure  can  vary  anywhere  between  these  two  extremes. 
A  common  dark  colored  variety  of  this  kind  of  rock  is 
called  basalt.  There  are  many  varieties  of  igneous  rocks, 
but  they  need  not  be  considered  here. 

The  sedimentary  rocks  are  those  that  are  made  by 
deposition  in  water.  When  rocks  are  wrorn  away  into 
fragments  and  these  fragments  are  deposited  in  water 


78  FIRST   TEAR   SCIENCE 

'  •  /* 

they  will,  under  certain  conditions,  harden  into  rocks. 
The  shells  and  remains  of  sea  animals  also  accumulate, 
and  after  a  time  consolidate  into  rock. ».  The  remains  of 
plants  may  accumulate  under  such  conditions  that  they 
will  not  rot  but  will  solidify  into  rock  which  we  call 
bituminous  or  soft  coal.  About  four  fifths  of  the  land 
surface  of  the  earth  is  composed  of  sedimentary  rocks. 
They  vary  greatly  in  color,  durability  and  usefulness 
to  men. 

The  sandstones,  which  are  composed  of  little  grains  of 
sand  cemented  together,  are  used  for  buildings  and  for 
many  other  purposes.  The  limestones,  which  are  mostly 
made  from  the  remains  of  sea  animals,  are  the  source  of 
our  lime  and  are  also  used  for  building  and  for  other  pur- 
poses. The  shales  are  finely  stratified  mud  deposits  often 
having  many  layers  in  an  inch  of  thickness.  Bituminous 
coal,  which  is  formed  from  plants  of  former  ages,  is  the 


OIL  WELLS. 
Tapping  the  rock  layers  containing  petroleum. 

most  useful  and  valuable  of  all  mineral  products.     None 
of  these  rocks  is  crystalline.     They  are  composed  of  frag- 


STRUCTURE  OF  LAND  AREAS 


79 


ments  of  other  rocks  or  remains  of  plants  or  animals  and 
usually  occur  in  layers  or  strata. 

Petroleum  is  probably  a  result  of  the  accumulation  in 
the  sea  of  layers  of  animal  and  plant  remains.  These 
were  covered  by  other  layers  and,  during  the  ages  since 
their  formation,  they  have  decomposed  and  changed  into 
oil  and  gas. 

The  metamorphic  rocks  have  a  crystalline  structure, 
often  contain  well-formed  crys- 
tals imbedded  in  them  and 
often  bands  of  crystalline  sub- 
stances extending  through 
them.  These  rocks  are  not  in 
the  condition  in  which  they 
were  originally  laid  down,  but 
are  modified  forms  of  either 
the  igneous  or  sedimentary 
rocks.  The  rocks  originally 
laid  down  have  been  subjected 
to  changes  which  have  rearranged  their  mineral  con- 
stituents and  changed  the  structure. 

These  changes  are  generally  due  to  heat  and  pressure. 
Marble  is  a  crystallized  limestone  and  gneiss  generally  a 
metamorphosed  granite.  Slate  and  mica-schist  are  greatly 
changed  clay  rocks  and  anthracite  coal  is  a  metamorphosed 
form  of  bituminous  coal.  The  rocks  of  this  group  are 
often  hard  to  distinguish  from  igneous  rocks. 

41.  Structure  of  the  Land  Areas.  —  Experiment  40.  —  Take  a 
copper  ball  having  a  ring  just  large  enough  to  encircle  it,  the  same 
apparatus  as  used  in  Experiment  19.  (Fig.  22.)  Place  the  ball 
within  the  ring  and  heat  them  both  to  a  high  temperature.  Remove 
the  ball  from  the  ring  and  plunge  it  into  a  dish  of  water.  Place  the 
cooled  ball  again  within  the  ring.  The  ring  will  be  found  too  large 
to  fit  snugly  upon  it. 

If  the  ring  had  been  a  cold  hollow  sphere  fitting  tightly  to  the  sur- 


GNEISS. 

Probably  metamorphosed 
granite. 


80 


FIRST   YEAR   SCIENCE 


face  of  the  hot  ball  and  the  ball  had  then  been  cooled  until  its  tem- 
perature approached  the  temperature  of  the  cold  surrounding  spherical 
surface,  it  would  have  shrunk  away  from  this  spherical  surface.  This 
would  leave  an  unfilled  space  between  the  two  into" which  the  spherical 
shell  must  have  shrunk  if  not  strong  enough  to  support  itself.  This 
shrinking  woiild  cause  wrinkling  in  some  parts  of  its  surface. 

Experiment  41.  —  When  at  home  measure  the  greatest  and  least 
circumference  of  a  large  smooth  apple  by  winding  a  string  around  it 
and  then  unwinding  and  measuring  the  length  of  the  string.  Bake  the 
apple.  Measure  its  circumferences  again.  Are  they  greater  or  less 
than  before  ?  Is  the  skin  of  the  apple  as  smooth  as  it  was  before  ? 

Not  only  do  the  land  areas  differ  greatly  in  the  kind  of 
rocks  of  which  they  are  composed,  but  also  in  the  way  in 
which  these  rocks  are  placed.  Some  of  the  rocks  lie  nearly 


STRATIFIED  ROCK. 
These  layers  have  remained  horizontal  as  originally  formed. 

in  the  condition  in   which  they   were  originally   formed 
while  others  have  been  folded  and  warped  and  twisted. 


STRUCTURE  OF  LAND  AREAS 


81 


Vast  layers  of  rocks  have  been  worn  away  by  the  forces 
which  are  continually  wearing  away  and  removing  the 
rocks  at  the  surface  of  the  earth,  and  thus  rocks  which 
were  once  at  great  depths  below  the  surface  have  been  ex- 
posed. Even  granite  rocks  which  were  originally  formed 
at  a  depth  of  thousands  of  feet  below  the  surface  now  ap- 
pear at  the  surface  and 
are  being  quarried  in 
many  places. 

The  folding  and  warp- 
ing of  the  rock  layers 
has  brought  some  of  the 
stratified  beds  which 
were  originally  horizon- 
tal into  an  almost  verti- 
cal position  so  that  we 
now  find  at  the  surface 
the  worn-off  edges  of 
these  beds.  The  dif- 
ferent kinds  of  rocks 
and  the  different  posi- 
tions in  which  the  rock  layers  are  presented  to  the  forces 
which  are  active  in  wearing  them  away  cause  great  variety 
in  the  forms  of  the  surface  features. 

It  is  not  necessary  to  consider  all  the  causes  which  may 
have  disturbed  the  position  of  the  rock  layers,  but  the 
most  important  of  them  deserves  attention.  It  has  already 
been  found  that,  although  the  exterior  of  the  earth  is  cool, 
the  interior  is  hot.  Now  it  is  known  that  almost  all  sub- 
stances contract  when  cooled.  If  the  interior  of  the  earth 
is  cooling,  and  there  is  every  reason  to  believe  that  it  is, 
then  it  must  be  contracting.  As  the  crust  is  already  cool 
it  has  ceased  to  contract  and  thus  the  interior  shrinks 
away  from  it  and  it  must  fold  up  in  order  still  to  rest 


FOLDED  ROCKS. 

Stratified  rocks  which    have  been  folded 
since  they  were  formed. 


82 


FIRST   YEAR   SCIENCE 


upon  the  shrinking  interior.  The  cooling  of  the  earth  is 
so  slow  that  the  folding  under  ordinary  conditions  disturbs 
the  surface  but  little.  ». 

42.    Rock   Weathering.  —  Experiment  42.  —  Weigh    carefully  a 
piece   of  dry  coarse   sandstone   or   coquiria.     Allow  this  to  remain 

in  water  for  several  days. 
Wipe  dry  and  weigh  again. 
Why  has  there  been  a 
change  in  weight  ? 

Experiment  43.  — Fill  a 
test'  tube  or  small  glass  dish 
about  half  full  of  limewater, 
made  by  putting  about  2 
ounces  of  quicklime  into  a 
pint  of  water.  Blow  from 
the  mouth  through  a  glass 
tube  into  the  limewater. 
There  is  formed  in  the  lime- 
water  a  white  substance 
which  chemists  tell  us  is  of 
the  same  composition  as 
limestone. 


ROCKS  WEATHERING  AND  FORMING  DEEP 
SLOPES. 


Experiment  44.  —  Con- 
tinue to  blow  from  the 
mouth  for  a  considerable 
time  through  a  tube  into  a  dish  of  limewater.  The  white  sub- 
stance disappears.  A  gas  in  our  breath  called  carbon  dioxide  dis- 
solves in  the  water,  forming  a  weak  acid  and  causes  the  change. 
Now  if  we  heat  the  water,  thus  decomposing  the  acid  and  driving 
out  the  gas,  the  white  sub |tance  again  appears.  This  gas  is  found 
everywhere  in  the  air  and  is  given  out  in  the  decay  and  burning  of 
substances. 

Rocks  which  are  exposed  to  the  atmosphere,  especially 
in  moist  climates,  undergo  decomposition.  If  the  climate 
is  warm  and  dry,  rocks  may  stand  for  hundreds  of  years 
without  apparent  change,  whereas  the  same  rock  in  another 


ROCK   WEATHERING 


83 


locality,  where  the  weather  conditions  are  different,  will 
crumble  rapidly.  A  striking  example  of  this  is  found  in 
the  great  stone  obelisk,  called  Cleopatra's  Needle,  which 
was  brought  from  Egypt  to  Central  Park,  New  York, 
some  time  ago.  Although  it  had  stood  for  3000  years  in 

Egypt    without    losing    ( 

the  distinctness  of  the 
carving  upon  it,  yet  in 
the  moist  and  change- 
able climate  of  New 
York  it  was  found  nec- 
essary within  a  year  to 
cover  its  surface  with  a 
preservative  substance. 
Not  only  do  different 
climates  affect  differ- 
ently the  wearing  away 
of  rocks,  but  different 
kinds  of  rocks  them- 
selves vary  much  in 
the  rate  at  which  they 
crumble.  It  has  been 
found  that  while  mar- 
ble inscriptions,  in  a 
large  town  where  there 

is  much  COal  smoke  and    CLEOPATRA'S    NEEDLE,    CENTRAL   PARK, 

.  NEW  YORK. 

considerable    ram,    will 

become  illegible  in  fifty  years,  that  after  a  hundred  years 
inscriptions  cut  in  slate  are  sharp  and  distinct. 

Experiment  45.  —  Allow  a  test  tube  filled  with  water  and  tightly 
corked  to  freeze.  What  happens  ?•  If  the  temperature  of  the  air  is 
not  cold  enough,  place  the  test  tube  in  a  mixture  of  chopped  ice  and 
salt,  or  better,  chopped  ice  and  ammonium  chloride  (sal  ammoniac), 
and  allow  it  to  remain  for  some  time. 


84 


FIRST   YEAR   SCIENCE 


Water  getting  into  the  cracks  of  rocks  and  expanding 
when  it  freezes  splits  them  apart  and  aids  much  in  their 

destruction.  Plant 
roots  penetrate  into  the 
crevices  of  rocks  and  by 
their  growth  split  off 
pieces  of  the  rock. 
Water,  especially  when 
it  has  passed  through 
decaying  vegetable  mat- 
ter, has  the  power  of 
dissolving  some  rock 
minerals.  Certain  min- 
erals of  which  rocks  are 
composed  change  when 
exposed  to  the  air  some- 
what as  iron  does  when 
it  rusts. 

,  Where  the  temperature  varies  greatly  during  the  day 
the  expansion  and  con- 
traction due  to  the  heat- 
ing and  cooling  some- 
times cause  a  chipping 
off  of  the  rock  surfaces. 
In  some  localities,  the 
winds,  by  blowing  sand 
particles  against  the 
rocks,  cut  them  away 
quite  rapidly.  All  these 
agencies  and  others  tend 
to  break  up  and  decom- 
pose the  rocks,  thus 
forming  soil.  The  actions  of  some  of  these  agencies  were 
seen  in  the  previous  experiments. 


ROCKS  SPLIT   BY  ROOTS  OF  A  TREE. 


WIND-CUT  ROCKS. 

These  rocks  have   been   fantastically  cut 
by  wind-blown  sand. 


S  OIL 


85 


43,  Soil.  —  Experiment  46.  —  Into  a  16  oz.  bottle  nearly  full  of 
water  put  a  small  handful  of  sand,  and  into  another  bottle  about  the 
same  amount  of  pulverized  clay.  Shake  each  bottle  thoroughly  and 
allow  the  water  to  settle.  Which  settles  the  more  rapidly?  Which 
would  settle  first  if  washed  by  a  stream  whose  current  was  gradually 
checked  ? 

Wherever  the  inclination  is  not  too  steep,  we  find  the 
surface  of  the  bed  rocks  covered  for  varying  depths  with 
a  loose  material  which  we  call  soil.  It  is  upon  this  that 
plants  grow  and  in  it  lies  the  wealth  of  our  agricultural 
communities.  On  examining  this  soil,  it  will  be  found 
that  in  some  places  it  grows  coarser  and  coarser  the  far- 


LOCAL  SOIL. 
This  soil  is  being  weathered  from  the  underlying  rock. 

ther  down  we  dig.     The  coarser  the  pieces  become,  the 
more  they  resemble  the  bed  rock,  until  finally  they  pass 


86 


FIRST   YEAR   SCIENCE 


by  imperceptible  stages  into  it.    .  This  kind  of  soil  is  called 
local  or  sedentary  soil. 

In  other  localities  the  coarseness  of  the  soil  does  not 
materially  change  as  we  dig  into  it,  but  suddenly  we  come 
upon  the  surface  of  the  bed  rock,  which  may  contain  few 
if  any  of  the  constituents  which  were  in  the  soil.  This 
soil,  which  in  no  way  resembles  the  underlying  rock,  is 
called  transported  soil.  We  shall  find  out  later  how  most 
of  it  reached  its  present  position. 


DIGGING  PEAT  IN  IRELAND. 
Peat  is  cut  in  small  brick-like  squares  and  dried,  before  being  used  as  fuel. 

The  first  kind  of  soil  has  evidently  been  made  in  some 
way  from  the  rock  below,  since  it  gradually  shades  into 
this  rock.  This  kind  of  soil  changes  with  the  change  of 
the  bed  rock.  A  striking  illustration  occurs  in  Kentucky, 
where  the  rich  and  fertile  "  Blue  Grass  "  region  is  bounded 


SOIL 


87 


by  the  poor  and  sandy  "Barrens."     The  one  is  underlaid 
by  limestone  and  the  other  by  sandstone.        / 

The  soil  at  the  surface  is  usually  finer  than  the  soil  a 
foot  or  so  below  the  surface,  and  sometimes  it  has  a  great 
deal  of  decayed  vegetable  matter  mixed  with  the  decom- 
posed rock,  and  to  this  its  fertility  is  often  largely  due. 
Some  soils  are  made  up  almost  entirely  of  decayed  vege- 
table matter,  peat  and  muck.  The  underlying  coarser 
and  lighter  colored  soil,  which  contains  little  if  any  vege- 
table matter,  is  usually  called  the  subsoil. 

Experiment  47. —  Examine  under  a  strong  magnifying  glass 
samples  of  sand,  loam,  clay,  peat  and  other  kinds  of  soil.  Notice  the 
different  kinds  of  particles  composing  the  different  soils  and  the 
shapes  of  these  particles. 

Experiment  48.  —  Put  a  handful  of  ordinary  loamy  soil  into  a  fruit 
jar  nearly  full  of  water  and  allow  it  to  stand  for  a  day  or  two,  shaking 
occasionally.  At  the  end  of  this 
time  shake  very  thoroughly  and 
after  allowing  it  to  settle  for  a 
minute,  pour  off  the  muddy  water 
into  another  jar.  Allow  this  to 
stand  for  about  an  hour  and  then 
pour  off  the  roily  water  and  evap- 
orate it  slowly,  being  careful  not 
to  burn  the  material  left.  Ex- 
amine with  the  eye,  by  rubbing 
between  the  thumb  and  fingers, 
and  with  a  magnifying  glass,  the 
three  substances  thus  separated. 
These  three  separates  will  be 
composed  largely  of  sand,  silt 
and  clay. 

If  a  compound  microscope  is     Jj 
available,  mix  a  bit  of  the  silt  and 
of  the  clay  in  a  drop  of  water  and  pj     43 

put   these  drops   on  glass  slides. 

Examine  the  drops  under  the  low  power  of  the  microscope.     Notice 
the  little  black  particles  of  decayed  vegetable  matter,  also  the  little 


88  FIRST   YEAR   SCIENCE 

jit 

bunches  of  particles  that  may  still  cling  together.  Why  was  it  neces- 
sary to  soak  the  soil  so  long  ?  Draw  the  shapes  of  a  few  of  the  par- 
ticles. Describe  the  composition  of  the  soil  you  have  examined. 

I. 

If  we  examine  most  soils  with  a  microscope,  we  shall 
find  that  they  are  composed,  as  was  seen  in  Experiment  48, 
of  many  different  kinds  of  material.  Some  of  these  mate- 
rials dissolve  slowly  in  water  and  thus  furnish  food  for 
plants  ;  others  are  insoluble. 

In  different  soils  the  particles  vary  greatly  in  size  as 
well  as  in  composition.  In  gravel  the  particles  are  large 
and  in  a  gram's  weight  there  would  be  but  few ;  in  sands 
there  are  many  more,  dependent  upon  the  fineness ;  and 
in  a  gram  of  clay  there  are  several  billion  particles.  Ag- 
ricultural soils,  intermediate  between  sand  and  clay,  are 
usually  called  loams.  There  are  sandy  loams  and  clayey 
loams,  with  many  intermediate  varieties.  As  the  mineral 
part  of  the  soil  is  derived  entirely  from  the  rocks,  only 
those  minerals  which  were  present  in  the  underlying  rock 
can  be  present  in  sedentary  soils,  whereas  in  transported 
soils  the  underlying  rock  has  had  no  influence  upon  the 
soil. 

The  minerals  composing  the  soil  must  furnish  certain 
substances  if  the  soils  are  to  support  plants.  The 
substances  needed  in  most  abundance  are  nitrogen, 
phosphoric  acid,  potash  and  lime.  Practically  all  soils 
except  the  quartz  sands  contain  more  or  less  of  these 
substances. 

The  chemical  make-up  of  the  rock  is,  however,  only  one 
of  the  qualities  necessary  for  it  to  support  plant  life.  It 
must  contain  water.  Plants  require  a  very  great  deal  of 
water.  Yet  few  plants  absorb  the  proper  amount  of  water 
if  they  are  submerged  in  it,  or  even  if  their  roots  are  sub- 
merged. They  must  have  the  soil  only  partly  saturated 
with  water. 


SOIL  89 

Experiment  49.  —  Take  about  a  quart  of  soil  from  a  few  inches 
below  the  surface  of  the  ground  and  after  sifting  out  the  large  chunks, 
put  it  in  a  sheet  iron  pan  and  carefully  weigh  it  to  the  fraction  of  a 
centigram.  Place  the  pan  containing  the  soil  in  a  drying  oven  or 
ordinary  oven,  the  temperature  of  which  is  but  little  above  100°  C. 
The  soil  should  be  spread  out  as  thin  as  possible.  Allow  it  to  remain 
in  the  oven  for  some  time,  until  it  is  perfectly  dry  throughout. 
Weigh  again.  The  loss  of  weight  will  be  the  weight  of  water  con- 
tained in  the  soil.  As  there  was  no  free  water  in  the  soil  how  was 
this  water  held?  Dip  your  hand  into  water  and  notice  how  the  water 
clings  to  it  after  it  is  withdrawn.  Examine  with  the  eye  and  the  lens 
several  particles  of  the  original  sdil  as  taken  from  the  ground  and  see 
if  there  is  a  water  film  on  each  of  these  as  there  was  on  the  wet  hand. 

Experiment  50.  —  Take  the  soil  after  it  was  dried  and  weighed  in 
the  previous  experiment  and  heat  it  throughout  to  a  red  heat  over  a 
Bunsen  burner  or  in  a  very  hot  oven.  Weigh  again.  If  there  is  still 
a  loss  of  weight  this  must  be  due  to  the  burning  of  the  organic  mat- 
ter, rotten  twigs,  roots,  leaves,  etc.,  which  was  in  the  soil.  Soils  differ 
greatly  in  the  amount  of  water  they  contain  and  in  the  amount  of  or- 
ganic substance  present. 

We  have  seen  from  Experiment  49  how  the  soil  takes 
up  water,  and  how  each  little  particle  has  a  film  of  water 
around  it.  Little  hairs  on  the  plant  roots  are  prepared 
to  take  up  these  little  films  of  water  which  surround 
the  soil  particles.  These  water  films  have  probably  dis- 
solved a  minute  amount  of  material  from  the  soil  particles, 
and  this  material  enters  into  the  plant  and  can  be  used 
for  food. 

Experiment  51.  —  Fill  an  8  oz.  bottle 
with  soil  taken  from  a  few  inches  be- 
low the  surface.  Fit  the  bottle  with  a 
two-hole  rubber  stopper  having  the 
long  neck  of  a  three  or  four  inch  fun- 
nel pushed  as  far  as  possible  through 
one  hole  and  a  bent  delivery  tube  just  Fig.  44. 

passing  through   the  other  hole.     See 

that  there  is  no  air  space  between  the  soil  and  the  stopper.     The 
soil  in  the  bottle  should  be  as  hard  packed  as  it  was  originally  in 


90 


FIRST   YEAR   SCIENCE 


the   ground.      If   necessary,   push   a  wire   down   through   the  neck 
of  the  funnel  so  as  to  free  all  hard-packed  particles  of  soil  in  it. 

Connect  the  delivery  tube  with  a  bottle  full,  of  water  standing 
inverted  on  the  shelf  of  a  pneumatic  trough.  Pour  water  into  the 
funnel  until  it  is  full,  and  keep  it  full  during  the  rest  of  the  experi- 
ment. Allow  the  apparatus  thus  arranged  to  stand  for  some  hours. 
Air  will  collect  in  the  bottle  over  the  pneumatic  trough.  Where  did 
it  come  from  ?  When  the  soil  in  the  bottle  has  become  entirely  satu- 
rated with  water,  roughly  compare  the  amount  of  air  collected  with 
the  volume  of  the  bottle  containing  the  soil.  What  part  of  the  soil's 
volume  is  the  air  ? 

The  smaller  the  soil  particles  are,  the  more  surface  they 
present  to  -water,  the  more  they  are  dissolved,  the  more 
food  the  plant  hairs  can  reach,  and  the  more  fertile  is  the 
soil,  other  things  being  equal.  We  have  also  seen  by  ex- 
periment that  soil  contains  air  as  well  as  water.  Air  is 
needed  if  plants  are  to  flourish,  and  it  is  necessary  that  it 
be  changed  frequently,  just  as  it  is  necessary  to  change 

the  air  in  a  room  if 
people  are  to  flourish. 
The  soil  must  be  ven- 
tilated. Plant  roots 
must  have  air  to  breathe. 
44.  Fertile  Soils. — 
Rock  disintegration 
does  not  furnish  all  the 
complex  materials 
needed  for  the  growth 
of  agricultural  plants. 
Only  the  lower  orders  of 
plants,  such  as  lichens, 
can  grow  on  soil  as  at 


MOLEHILLS. 

Showing  how  animals  dig  up  the  soil  and 
make  it  porous. 

first  formed.     A   fertile   soil  is  the  product  of  ages  of 
plant  and  animal  life,  labor  and  decay. 

Plants  send  their  filaments  and  roots  among  the  rock 


FERTILE  SOILS 


91 


particles,  prying  open  their  crevices  and  pushing  the 
pieces  apart  so  that  the  agents  of  disintegration  can  more 
readily  attack  them.  By  their  decay  plants  provide  the 
humus  so  necessary  for  making  soil  fertility. 

Animals  like  moles  and  gophers  plow  their  holes  through 
the  soil,  mixing  up  the  particles  and  making  the  soil  porous, 
so  that  the  water  can 
readily  get  in  to  aid  in 
breaking  up  and  decom- 
posing the  soil  particles. 
These  holes  also  provide 
openings  through  which 
plant  roots  and  soil  or- 
ganisms can  obtain  the 
oxygen  and  dissolved 
food  they  need.  Ants 
each  year  move  vast 
quantities  of  fine  mate- 
rial to  the  surface,  and 
in  some  places  change  the  surface  soil  in  a  few  years. 

Angleworms,  the  most  important  animal  soil  builders, 
channel  the  soil  with  their  burrows,  thus  providing  ready- 
made  openings  for  the  growing  roots  and  by  increasing 
the  porosity  of  the  soil  aid  in  its  ventilation  and  drainage. 
They  swallow  the  soil  as  they  make  their  burrows,  in 
order  to  get  the  decaying  vegetable  matter  for  food,  and 
they  grind  it  fine  as  it  passes  through  their  bodies.  Every 
year  they  bring  to  the  surface  great  quantities  of  this 
finely  ground  soil  mixed  with  the  undigested  vegetable 
matter.  Darwin  estimated  that  the  angleworms  in  Eng- 
lish soil  deposited  one  fifth  of  an  inch  of  these  castings 
each  year  over  some  parts  of  the  surface.  This  is  the 
finest  kind  of  fertilizer.  It  is  a  common  saying  that  the 
more  angleworms  the  better  the  soil. 


ANTHILL. 

This  soil  has  been  brought  from  below  and 
piled  up  by  the  ants. 


92 


FIRST   YEAR   SCIENCE 


Besides  harboring  these  visible  plants  and  animals  the 
soil  teems  with  germ  life.  Some  of  these  germs  increase 
the  fertility  of  the  soil  and  some  decrease  it.  It  has  been 
estimated  that  there  are  50,000  germs  of  various  kinds  in 
a  gram  of  fertile  soil.  It  is  these  that  cause  the  decay 
of  the  vegetable  and  animal  matter  in  the  soil.  In  the 
course  of  this  decay  various  acids  and  gases  are  formed 


MUD  CRA.CKS. 
Showing  the  way  clay  cracks  when  it  dries. 

which  help  to  decompose  the  rock   particles  and  other 
compounds  which  are  needed  for  the  food  of  the  plants. 

The  most  important  of  these  germs  to  agriculture  are 
the  nitrogen-fixing  bacteria.  Plants  must  have  nitrogen 
if  they  are  to  grow,  but  they  are  unable  to  take  it  from 
the  air  where  it  exists  in  greatest  abundance.  For  the 
use  of  the  plants  it  must  be  chemically  combined  with 
other  substances  and  these  compounds  must  be  soluble  in 
water.  Saltpeter  is  a  compound  of  this  kind  and  is  often 


AGRICULTURAL   SOILS  93 

used  to  fertilize  plants.  But  soluble  compounds  of  nitro- 
gen are  not  abundant,  and  these  would  be  soon  removed 
from  many  soils  unless  in  some  way  replaced. 

This  is  most  often  done  by  adding  manures  to  the  soil. 
In  these  there  are  nitrogen  compounds  which  the  bacteria 
of  the  soil  work  over  and  get  into  shape  so  that  the  plants 
can  use  them.  Some  bacteria  are  even  able  to  take  the 
nitrogen  from  the  soil-air  and  combine  it  so  that  it  can  be 


LUMPY  SOIL. 
The  result  of  cultivating  at  the  wrong  time. 

used  by  the  plants.  If  this  varied  and  teeming  life  of  the 
soil  is  to  thrive,  certain  conditions  must  be  maintained, 
and  it  is  the  skill  of  the  agriculturist  in  maintaining  and 
increasing  these  favorable  conditions  which  determines  his 
success  or  failure. 

45.  Agricultural  Soils.  —  As  has  already  been  shown,  soils 
differ  greatly  in  fineness,  mineral  composition  and  water- 
holding  capacity.  They  also  differ  greatly  in  the  amount 
of  decayed  vegetable  material  or  humus  in  them.  The 
humus  is  a  most  important  soil  ingredient.  It  helps  in 


94 


FJRST   YE  An   SCIENCE 


holding  water,  it  furnishes  plant  food  and  it  keeps  the 
soil  from  getting  too  compact. 

In  sandy  soils  there  is  usually  little  humus,  the  water 
soon  drains  out  of  them  and  plants  become  parched.  Such 
soils  warm  up  quickly  in  the  spring  and  dry  out  rapidly 
after  long  wet  spells.  When  humus  and  plant  food  in 

the  form  of  manure  are 

added  they  are  especially 
adapted  for  growing 
early  crops  and  crops 
that  do  not  require  a 
great  deal  of  moisture, 
such  as  grapes.  The 
"  Fresno  Sand  "  of  Cali- 
fornia and  the  sandy 
coast  plains  of  the  east- 
ern United  States  are 
soils  of  this  kind. 

In  clay  soil  the  parti- 
cles are  extremely  small, 
as  are  also  the  spaces 
between  the  particles. 
Water  is  therefore  taken 
up  very  slowly.  It  is, 
however,  held  tena- 
ciously. When  clays 

become  wet,  they  are  very  sticky  and  cannot  be  worked. 
When  they  dry,  they  become  very  hard  and  crack. 
If  cultivated  at  the  wrong  time  they  break  into  hard 
lumps  and  render  further  cultivation  difficult.  The 
adobe  soil  of  the  west  is  of  this  character.  If  the  soil  is 
nearly  pure  clay,  it  is  useless  for  farming.  If  sufficient 
sand  or  humus  can  be  added,  it  becomes  valuable,  since 
clays  usually  contain  the  elements  needed  by  plants. 


ADOBE  SOIL. 

A  heavy  clay  soil,  very  fertile,  but  hard 
to  cultivate. 


AGRICULTURAL   SOILS 


95 


A  soil  having  grains  about  midway  in  size  between  sand 
and  clay  is  called  a  silt.  This  is  usually  a  most  fertile 
soil.  It  is  the  soil  of  the 
western  prairies  and  the 
great  grain-producing 
states  of  our  country. 
It  holds  water  well,  con- 
tains an  abundance  of 
plant  food,  and  is  easily 
cultivated.  Between 
these  three  types  —  sand, 
silt  and  clay  —  there  are 
all  grades  of  soils  pre- 


senting problems  of  vari-   THE   CRACKING   OF   ADOBE   SOIL  WHEN 
ous  degrees.     The  prob-  DRY- 

lem  $f  the  farmer,  however,  is  to  maintain  a  soil  which 
holds  water  but  is  well  drained,  which  contains  the  ele- 


PBAIBIE  SCENE. 
Showing  modern  methods  of  harvesting  the  crops  from  the  fertile  silt  soil. 

ments  plants  need,  and  which  is  mellow  enough  to  be  well 
aired  and  to  let  the  plant  roots  grow. 


96 


FIRST   YEAR   SCIENCE 


46.  Soil  Water.  —  Although  many  soils  contain  every- 
thing needful  for  the,  production  of  agricultural  plants, 
yet  the  rainfall  is  insufficient  or  so  unevenly  distributed 
that  these  plants  are  unable  to  grow.  This  is  true  over  a 
large  area  of  the  United  States,  and  the  same  conditions 
often  prevail  over  the  usually  well  watered  part  of  the 
country  in  times  of  drought.  The  question  of  increasing 
the  water-holding  capacity  and  of  preventing  the  loss  of 
water  by  evaporation  or  in  other  ways  is  a  very  important 
one. 

Experiment  52.  —  Weigh  out  equal  amounts  (about  100  g.  each)  of 
dried  gravel,  coarse  sand  and  very  fine  sand.  Put  each  of  these  into 
a  four -inch  funnel  which  has  been  fitted  with  a  filter  paper.  Pour 
water  upon  each  until  all  that  can  be  absorbed  has  been  absorbed. 
Allow  each  to  stand  until  water  ceases  to  drop  from  the  funnel. 
Weigh  again,  balancing  the  weight  of  the  wet  filter  paper  retainer  by 
a  similar  wet  filter  paper  placed  on  the  weight  side  of  the  scales.  Which 
of  these  substances  is  capable  of  holding  the  most  water?  Since 

water  does  not  penetrate 
into  the  grains  composing 
these  different  substances 
the  difference  in  water  hold- 
ing capacity  must  be  due  to 
the  different  sizes  of  the 
grains. 

If  we  dig  deep  enough 
into  almost  any  soil  we 
shall  find  water.  Wells 
show  this.  Certain  trees 
and  plants  have  such 
long  roots  that  they  can 
reach  the  underlying 
water  and  flourish  where 


ALFALFA  ROOT. 

A  long  root  which  has  gone  deep  to  seek 
water. 


other  plants  will  die.     When  wet  lands  are  so  drained 
by  tiling  that  the  plants  can  send  their  long  roots  down 


SOIL    WATER 


97 


to  this  constant  water  supply  or  water  table,  as  it  is 
called,  they  stand  a  drought  much  better  than  plants 
grown  on  undrained  land  where  the  water  table  has 
not  so  uniform  a  depth. 

Experiment  53.  —  Place  small  glass  tubes  of  several  different  bores 
in  a  dish  of  colored  water.  In  which  is  the  surface  of  the  water 
higher,  in  the  tubes  or  in  the  dish?  In  which  tubes  is  it  the  higher, 
those  of  large  or  small  bore  ? 

Experiment  54.  — Place  two  wide-mouth  4  oz.  bottles  side  by  side 
and  fill  one  partly  full  of  water.  Put  a  coarse  piece  of  cloth,  or  better, 
a  lamp  wick,  into  the  water  bottle  and  allow 
the  other  end  to  hang  over,  into  the  empty 
bottle.  Allow  the  bottles  to  stand  thus  for  an 
hour.  What  happens?  The  force  that  causes 
the  rising  of  water  up  small  tubes,  wicks  and 
crevices  is  called  capillarity. 


Fig.  45. 


Experiment   55.  —  Tie   pieces   of   cloth   over 

the  ends  of  four  lamp  chimneys.     Fill   one   of 

the  chimneys  with  coarse  sand,  another  with 

fine  sand,  another  with  clay,  and  the 
fourth  with  a  deep  black  loam.  Stand 
each  chimney  in  a  shallow  pan  of  water. 
Allow  them  to  remain  for  a  week, 
keeping  water  in  the  pan  all  the  time. 
Note  how  high  the  water  has  risen  in 
the  different  chimneys  at  the  end  of 
an  hour ;  two  days ;  a  week. 

It  was  found  in  Experiment 

49  that  each  little  particle  of  soil  was  surrounded  by  a 
film  of  water,  even  though  there  was  apparently  no 
water  in  the  soil.  This  film  will  be  replaced  if  removed 
just  as  the  water  in  the  top  of  the  wick  (Experiment  54) 
was  replaced  by  water  flowing  up  the  wick.  Roots  get 
a  large  part  of  their  water  by  absorbing  the  water  films 
of  the  soil  particles. 

If  a  region  is  well  supplied  with  forests  so  that  the  rain 


98 


FIRST   YEAR   SCIENCE 


as  it  falls  is  held  by  the  moss,  leaves  and  roots  and  pro- 
tected from  evaporation  by  the  foliage,  soil  water  will 
continue  to  be  supplied  to  the  surrounding  open  land  long 
after  it  would  have  become  dry  had  the  forests  been 
removed.  Mountain  soils  have  been  found  which  hold 
back  five  times  their  own  weight  of  water. 


A  NATURAL  SPRING. 
Coming  to  the  surface  between  rock  layers. 

Gravity  is  continually  pulling  the  soil  water  deeper  and 
deeper  into  the  ground.  This  deep  soil  water  is  frequently 
diverted  to  lower  ground  by  impervious  layers  of  soil  or 
rock  and  comes  to  the  surface  as  springs,  or  it  may  come 
gradually  to  the  surface  over  a  broad  area  a  long  distance 
away  from  where  it  fell  and  make  a  region,  otherwise 
barren,  fertile  by  subirrigating  it. 

It  is  often  very  essential  to  stop  as  far  as  possible  this 


SOIL    WATER 


99 


downward  passage  of  water,  or  seepage,  as  it  is  called. 
The  water  in  seeping  through  the  soil  dissolves  plant  food 
and  if  allowed  to  drain  off  would  decrease  the  fertility  of 
the  soil.  Whatever  decreases  the  porosity  of  the  soil  will 
decrease  the  seepage  and  thus  help  to  retain  the  plant 
food.  This  may  be  done  by  adding  humus,  and  sometimes 


AN  ARTESIAN  SPRING. 
A  deep  water-layer  has  been  pierced  and  the  water  diverted  to  the  surface. 

where  the  soil  is  very  porous  by  rolling.  At  the  time 
rain  is  likely  to  fall,  however,  the  soil  must  be  kept  loose 
and  mellow  so  that  the  water  can  sink  into  it. 

Evaporation  is,  however,  the  cause  of  soil's  losing  the 
greatest  amount  of  water.  Soil  water  is  constantly  mov- 
ing toward  the  surface  on  account  of  capillary  action,  and 
is  being  evaporated.  This  loss  by  evaporation  must  be 
counteracted,  if  in  arid  countries  or  during  dry  spells 


100 


FIRST  TEAR   SCIENCE 


agricultural   plants   are    to    be    provided   with   sufficient 
moisture. 

Experiment  66.  —  Fill  full  of  soil  four  tin  cans' having  small  holes 
punched  in  the  sides  and  bottom.  Water  each  with  the  same  amount 
of  water.  Cover  the  first  with  about  an  inch  of  grass  and  the  second 
with  about  an  inch  of  sawdust,  and  weigh  carefully.  Weigh  the  third 
and  fourth.  Record  the  weight  of  each.  Thoroughly  stir  the  sur- 
face of  the  third,  as  soon  as  it  is  dry  enough,  about  an  inch  deep. 
Keep  this  stirred.  Let  the  fourth  stand  undisturbed.  Weigh  all  four 
every  school  day  for  two  weeks.  Keep  a  record  of  the  loss  of  weight 
of  each.  Why  have  they  lost  weight  ?  How  do  the  grass,  the  saw- 
dust, and  stirring  of  the  earth  affect  the  loss  ?  Suggest  ways  to  keep 
soils  from  losing  their  moisture. 

In  Experiment  56,  it  was  seen  that  if  a  layer  of  grass 
or  sawdust  was  put  on  the  top  of  the  soil,  the  moisture  did 


DRY  FARMING"  IN  EGYPT. 


not  evaporate  as  rapidly  as  it  did  when  the  soil  was  not 
covered.  The  grass  could  have  been  replaced  by  shav- 
ings, manure,  or  any  substance  which  would  protect  the 


SOIL   WATER 


101 


ground  from  the  sun  and  wind.  Protections  of  this  kind 
are  called  mulches.  They  are  most  frequently  used  around 
trees,  vines  and  shrubs.  It  is  impracticable  to  use  them 
extensively  on  growing  crops. 

It  was  also  found  that  soil  water  was  not  readily  evapo- 
rated where  the^top  of  the  soil  was  kept  stirred,  so  that 
the  little  capillary  tubes  by  which  the  soil  water  reaches 
the  surface  were  broken  and  the  sunshine  and  air  were  kept 
from  the  under  part  of  the  soil  by  a  layer  of  finely  divided 
soil  mulch.  When  the  surface  of  the  soil  is  thoroughly 
stirred  or  cultivated  the  particles  are  separated  so  far 
apart  that  the  water  cannot  pass  from  one  grain  to  an- 
other, and  so  is  retained  in  the  under  layer  ready  for  the 
plant  roots.  Thorough  tillage  of  agricultural  crops  is 
perhaps  the  best  way  to  assure  the  plants  sufficient 

moisture  in  regions  subject  to i 

droughts. 

In  some  parts  of  the  arid 
region  of  the  United  States  dry 
farming  is  practiced.  The  soil 
is  deeply  plowed  and  the  plow 
often  followed  by  a  bevel  wheel 
roller  called  a  soil  packer,  in 
order  to  pack  the  under  soil  or 
subsoil  so  that  the  air  cannot 
circulate  through  it  and  dry 
out  the  upper  soil.  The  sur- 
face soil  is  then  most  thoroughly 
cultivated  so  as  to  make  as  per- 
fect a  soil  mulch  as  possible. 
Thus,  whatever  moisture  falls  is  kept  from  seeping  below 
the  reach  of  the  plant  roots  and  from  evaporating  from 
the  surface.  In  this  kind  of  farming  the  aim  is  to  usje 
more  than  one  year's  moisture  in  growing  a  crop. 


KAFFIR  CORN. 
A  plant  suitable  for  dry  farming. 


102 


SCIENCE 


Crops  are  usually  planted  only  every  other  year,  two 
years'  moisture  being  retained  for  one  crop.  The  soil  is, 
however,  kept  thoroughly  cultivated  all  the  time.  Of 
course  plants  requiring  the  least  amount  of  moisture  are 
best  adapted  to  dry  farming. 

Irrigation  is  the  most  efficient  means  of  raising  crops  in 
regions  of  insufficient  rainfall  or  of  droughts.  Water  is 


IRRIGATION  IN  SQUARES. 

brought  to  the  land  from  distant  sources,  or  from  flowing 
artesian  wells,  or  is  pumped  from  wells  which  have  been 
sunk  to  an  available  water  table.  In  this  way  water  can 
be  supplied  to  plants  whenever  needed.  Where  the 
ground  is  quite  level  it  is  often  flooded,  sometimes  in 
larger  or  smaller  squares,  with  little  ridges  separating  the 
squares.  A  great  deal  of  water  is  lost  in*  this  way  by 
eyaporation. 

Another  way  is  to  plow  furrows  eight  to  ten  inches 


ALKALI  SOILS  103 

deep  in  the  direction  of  the  surface  slope  and  run  the 
water  into  these  from  the  irrigation  ditch.  In  either 
case  the  water  is  allowed  to  soak  in  until  the  soil  is 
thoroughly  wet.  The  surface  is  then  cultivated  so  as  to 
check  surface  evaporation.  In  the  last  few  years  the 
government  and  many  private  companies  have  spent  mil- 
lions of  dollars  in  putting  in  irrigation  plants.  By  this 


IRRIGATION  IN  FURROWS. 

means  thousands  of  acres  of  land  which  would  otherwise 
have  been  valueless  for  agriculture  has  been  made  ex- 
ceedingly productive. 

47.  Alkali  Soils.  —  In  dry  regions  where  the  rainfall  all 
sinks  into  the  ground  and  after  remaining  for  a  time  rises 
to  the  surface  and  is  evaporated,  large  areas  are  found 
upon  which  almost  nothing  can  be  made  to  grow  even 
when  sufficient  water  is  provided.  Often  in  the  dry  sea- 
son white  or  brown  crusts  appear  scattered  over  the  sur- 


104 


FIRST  YEAR   SCIENCE 


face  in  large  patches.  The  white  crust  usually  tastes  like 
Epsom  salts  and  the  brown  like  salsoda.  The  salts  form- 
ing these  patches  have 
been  dissolved  out  of 
the  soil  by  the  soil 
water  and  left  on  the 
surface  when  it  evapo- 
rated. 

Such  substances  are 
not  found  in  wet  regions 
because  they  are  carried 
away  by  the  water  which 
runs  into  the  streams. 
About  the  only  way  soil 


-ALKALI   SOIL. 

Few  plants  can  grow  here  because  of  the 
excess  of  alkaline  salts. 


of  this  kind  can  be  treated  to  make  it  productive  is  to 
irrigate  and  drain  it,  thus  washing  the  salts  out  of  the 


RECLAIMING  ALKALI  SOIL  IN  THE  SAHARA. 

soil.  This  is  just  what  is  done  by  nature  in  well-watered 
regions.  Sometimes  if  there  is  not  much  alkali  deep 
plowing  or  the  planting  and  removal  of  certain  plants 


SOIL  AND  MAN 


105 


such   as   sugar  beets,  which  are  capable   of   growing   in 
such  soils,  will  sweeten  it. 


ROMAN  PLOWING. 
Showing  primitive  methods. 


48.   Soil  and  Man.  —  Although  nature  through  countless 
ages  has  been  preparing  the  soil,  and  generation  after  gen- 


STEAM  PLOW. 
Showing  modern  methods. 


eration  of  plants  and  animals  has  been  contributing  to  its 
fertility,  yet  it  will  not  continue  profitably  to  produce 


106  FIRST   YEAR   SCIENCE 

*  y* 

agricultural  crops  unless  carefully  handled  by  man.  The 
materials  taken  from  it  must  be  replaced  by  manures.  It 
must  also  be  thoroughly  tilled  in  order  (1)  to  keep  in  the 
moisture,  (2)  to  prepare  a  mellow  place  where  the  roots 
of  the  plants  may  spread,  (3)  to  provide  air  and  water 
and  humus  needed  by  the  germs  which  build  up  the  solu- 
ble nitrogen  compounds,  and  (4)  to  kill  the  weeds  which 
would  use  the  space  and  plant  foods  needed  by  the  grow- 
ing crops  and  would  choke  them  out.  Proper  tillage 
probably  has  more  to  do  with  thrifty  and  productive  farm- 
ing than  any  other  one  thing.  By  careful  tillage  much 
expense  for  fertilizers  can  be  saved  and  the  value  of  the 
crop  produced  greatly  increased. 


GOOD  SOIL. 
A  truck  farm. 

49.  Value  of  Soils.  —  Many  different  factors  enter  into 
the  determination  of  the  value  of  a  soil.  Soils  which  in 
one  locality  would  be  of  great  value  are  almost  valueless  in 
other  localities.  Light  sandy  soil  far  from  a  market,  un- 
less transportation  facilities  are  exceptionally  good,  is 


SUMMARY  107 

almost  worthless,  while  the  same  soil  near  a  city  where 
fertilizers  can  be  easily  procured  and  where  early  vege- 
tables find  a  ready  market  is  of  great  value. 

Different  soils  are  adapted  to  different  crops,  and  where 
a  soil,  although  not  good  for  many  crops,  is  adapted  for 
raising  a  crop  which  in  its  locality  is  valuable,  the  soil  is 
called  good.  Thus  the  soil  in  many  parts  of  Florida,  al- 
though unsuited  for  raising  most  crops,  is  suited  for 
orange  trees  and  early  vegetables,  and  so  is  a  good  soil. 
The  stony  soil  in  certain  of  the  orange  regions  of  Califor- 
nia would  be  an  exceedingly  poor  soil  for  most  crops,  but 
it  is  good  for  oranges  and  therefore  it  is  most  valuable. 

Summary.  —  Only  a  little  more  than  a  quarter  of  the 
earth's  surface  is  land,  and  only  a  little  over  a  twentieth 
of  this  land  belongs  to  the  United  States.  Though  there 
are  depths  in  the  ocean  greater  than  our  highest  moun- 
tains, most  sea  animals  live  near  the  surface,  while  land 
animals  are  distributed  over  hills  and  valleys.  This  gives 
greater  variety  to  life  on  land. 

Water  is  simply  a  compound  of  oxygen  and  hydrogen. 
It  has  many  valuable  and  interesting  properties :  it  is  prac- 
tically incompressible;  it  is  the  greatest  dissolver  of  sub- 
stances that  there  is;  it  evaporates  readily,  giving  us  rain, 
and,  when  put  under  pressure,  our  steam  power;  it  has 
great  power  of  taking  up  heat,  thus  regulating  the  climate 
of  the  land  near  which  large  bodies  of  it  lie. 

The  land  is  made  up  of  various  animal,  mineral  and 
vegetable  substances.  But  four  fifths  of  it  consists  of 
sedimentary  rocks,  that  is,  those  that  were  deposited  by 
water,  as  distinguished  f rom  igneous  or  rocks  formed  from 
melted  materials  within  the  earth,  and  metamorphic  or 
rocks  that  have  been  changed  from  sedimentary  or  igneous 
rocks. 


108  FIRST   YEAR   SCIENCE 

The  soil  comes  chiefly  from  the  decaying  and  weather- 
ing of  rocks.  It  is  divided  into  local  or  sedentary  soil, 
that  which  is  formed  from  the  rocks  directly  beneath  it, 
and  transported  soil,  that  which  is  generally  brought  down 
and  deposited  by  water,  ice  and  wind.  Soils  are  classed 
roughly  as  gravel,  sand,  clay,  and  loam. 

The  fertility  of  the  soil  depends  largely  upon  composi- 
tion, air  and  water,  ventilation  and  drainage.  Fertile  soil 
must  contain  nitrogen,  potash  and  lime.  The  roots  of 
plants  must  have  air  to  breathe,  and  water  must  dissolve 
the  nourishing  substances  in  the  soil  and  bring  them  to 
the  roots  to  be  absorbed.  For  this  reason  the  soil  should 
not  be  packed  hard  like  clay,  nor  should  it  be  loose  like 
coarse  gravel,  as  clay  does  not  let  the  water  soak  through 
readily,  while  gravel  lets  it  seep  down  too  fast. 

To  maintain  its  fertility,  the  soil  must  be  frequently  cul- 
tivated to  decrease  seepage  and  evaporation.  It  must  be 
supplied  with  fresh  nourishment  by  manures  or  other 
fertilizers.  In  some  districts  where  the  rain  supply  is 
inadequate,  irrigation  and  dry  farming  are  practiced. 
Different  soils  are  suited  to  different  crops.  Without 
the  fertility  of  the  soil,  life  on  the  earth  would  cease. 

QUESTIONS 

For  what  would  you  look  if  trying  to  determine  whether  a  land 
surface  had  ever  been  under  the  sea  ? 

What  are  the  characteristic  differences  between  land  and  water 
surfaces  and  between  the  conditions  to  which  the  animals  and  plants 
of  each  are  subjected  ? 

What  reasons  can  you  suggest  for  likening  the  earth  to  a  water 
engine  ? 

To  what  great  classes  do  the  rocks  in  your  neighborhood  belong? 

What  examples  of  rock  weathering  have  you  ever  seen  ?     Describe. 

Is  the  soil  in  your  neighborhood  local  or  transported?  Does  its 
character  vary  much  in  different  places?  Does  the  fertility  vary? 


SUMMARY  109 

What  would  you  suggest  as  the  causes  of  these  variations? 
What  is  necessary  to  produce  a  fertile  soil  ? 
How  can  the  fertility  of  a  soil  be  maintained? 
How  can  the  supply  of  soil  water  be  maintained  in  dry  regions  and 
at  times  of  drought  ? 

What  determines  the  value  of  a  soil  ? 


CHAPTER   V 


THE  ATMOSPHEKE  OF  THE  EAETH 

50.  The  Origin  of  the  Atmosphere.  —  As  the  earth  cooled 
down  from  the  intensely  hot  condition  which  it  is  supposed 
to  have  had  at  first,  the  substances  which  had  not  chem- 


BLUE  HILL  OBSERVATORY,  MILTON,  MASS. 

One  of  the  first  places  in  America  where  conditions  of  the  upper  atmosphere 

were  studied. 

ically  combined  and  formed  liquids  and  solids,  or  which 
required  a  low  temperature  for  their  consolidation  were 
left  still  in  the  gaseous  state  around  the  solid  core.  This 
gaseous  envelope  composed  of  these  substances  sur- 
rounding the  earth  we  call  the  atmosphere.  Some  of 

110 


COMPOSITION   OF  AIR  111 

these  gases  are  inert  and  do  not  readily  combine  with 
other  substances.  Others  have  formed  extensive  com- 
binations, but  they  exist  in  such  large  quantities  that  they 
were  not  thereby  exhausted. 

51.   The  Composition  of   the  Air.  —  Experiment  67.  — (To  be 
performed  only  by  the  teacher.)     Having  rounded  out  a  cavity  in  a 
small  flat  cork,  cover  the  cavity  and  surface  around 
it  with  a  thin  layer  of  plaster  of  Paris.     After  the 
plaster  has  set  and   become   thoroughly  dry  float 
the  cork  on  a  dish  of  water  with  the  cavity  side 
up.     Place   a   piece  of  phosphorus   as  large   as   a 
pea  in  the  cavity  and  carefully  light  it.     (Great  care 
must  be  taken  in  handling  phosphorus  as  it  ignites 
at  a  low  temperature  and  burns  with  great  fierce- 
ness.    It  must  always  be  cut  and  handled  under  Fig.  47. 
water.) 

As  soon  as  the  phosphorus  is  lighted,  cover  it  with  a  wide-mouthed 
bottle.  Be  sure  that  the  mouth  of  the  bottle  is  kept  slightly  under 
water.  The  water  will  be  found  to  rise  in  the  bottle.  The  phos- 
phorus soon  ceases  to  burn.  White  fumes  are  formed,  but  these 
soon  clear  up.  A  clear  gas  is  left  in  the  bottle,  but  this  cannot  be  air, 
for  if  it  were,  the  phosphorus  would  have  continued  to  burn  in  it,  since 
it  burns  in  air.  If  it  were  not  for  this  property  of  not  permitting 
phosphorus  to  burn,  the  gas  left  in  the  bottle  could  not  be  distinguished 
by  ordinary  means  from  air. 

The  gas  fills  more  than  three  fourths  of  the  bottle,  so  that  more 
than  three  fourths  of  the  air  is  composed  of  a  gas  which  does  not  sup- 
port combustion.  This  gas  is  called  nitrogen.  The  other  constituents 
of  the  air  must  also  be  transparent  colorless  gases,  since  the  air  is 
transparent  and  colorless.  The  most  important  of  these  is  called 
oxygen.  The  phosphorus  united  with  this  and  formed  the  white 
fumes.  These  fumes  dissolved  in  the  water,  leaving  the  nitrogen. 

Be  careful  to  put  the  cork  on  which  the  phosphorus  was  burned  in 
a  place  where  it  cannot  cause  a  fire. 

Although  the  air  appears  like  a  simple  gas  and  was  so  con- 
sidered until  the  end  of  the  eighteenth  century  it  has  been 
shown  to  be  composed  of  several  different  colorless  gases. 
One  of  these,  oxygen,  supports  combustion ;  another, 


112 


FIRST  TEAR   SCIENCE 


nitrogen,  neither  burns  nor  supports  combustion.  Chem- 
ists have  found  that  these  two  gases  are  mixed  in  the  air 
in  the  proportion  of  about  one  part  of  oxygen  to  four  parts 
of  nitrogen. 

Another  heavy  colorless  gas  called  carbon  dioxide  is 
found  in  the  air  in  the  proportion  of  about  3  parts  to 
10,000.  There  are  in  addition  very  small  quantities  of 
several  other  gases,  but  these  are  not  of  sufficient  impor- 
tance to  be  studied  here.  Besides  the  gases,  the  air  con- 
tains other  matter,  such  as  water  vapor,  dust  particles  and 
microbes. 

Experiment  58.  —  Obtain  four  bottles  of  oxygen  from  the  chemical 
laboratory.  If  not  obtainable,  place  a  piece  of  sodium  peroxide 
(oxone)  about  as  large  as  the  end  of  a  finger 
in  a  side  necked  test  tube  provided  with  a 
medicine  dropper  filled  with  water,  as  shown  in 
Fig.  48.  Put  the  end  of  the  delivery  tube 
under  the  mouth  of  an  inverted  bottle  filled 
with  water  arranged  on  the  shelf  of  a  pneu- 
matic trough.  Drop  water  slowly  on  to  the 
sodium  peroxide  and  collect  the  gas  gener- 
ated. Fill  several  bottles.  Oxygen  can  also 
be  prepared  by  heating  a  mixture  of  about 
one  part  manganese  dioxide  and  two  parts 
potassium  chlorate  in  a  test  tube  and  collect- 
ing the  gas  over  water  (Fig.  49).  Does  the 


Fig.  48. 


Fig.  49. 


appearance  of  this  gas  differ  in  any  way  from  air?     Smell  of  it. 
Has  it  any  odor?    Into  one  of  the  bottles  of  oxygen  insert  a  splinter 


COMPOSITION  OF  AIR  113 

of  wood  having  a  spark  at  the  end.  It  bursts  into  flame.  Does  the 
same  thing  take  place  when  the  stick  with  the  spark  upon  it  is 
held  in  a  bottle  of  air  ? 

Hold  a  lighted  match  at  the  mouth  of  another  of  "\ 

the  bottles  containing  oxygen.  Does  the  gas  itself 
burn  as  illuminating  gas  does  when  a  match  is 
applied  to  it?  If  the  oxygen  in  the  air  were  in- 
creased or  decreased,  it  would  have  a  great  effect 
upon  combustion.  Attach  a  piece  of  sulphur  to 
a  short  piece  of  picture  wire.  Ignite  it  and  place  Fig.  50. 

the  wire  in  a  bottle  of  oxygen  (Fig.  50).  Does  the 
sulphur  burn  strongly  ?  How  about  the  wire  ?  Does  it  burn  too  ? 

The  oxygen  is  the  most  important  part  of  the  air  to 
animals,  for  without  it  they  could  not  live.  They  breathe 
in  oxygen  and  breathe  out  carbon  dioxide.  All  their 
heat  and  energy  is  due  to  the  power  they  have  of  com- 
bining oxygen  with  carbon  and  forming  carbon  dioxide. 
Plants  also  need  it. 

Plants  need  carbon  dioxide  as  much  as  animals  need 
oxygen.  By  far  the  greater  part  of  plants  is  made  from 
the  carbon  which  they  get  from  this  gas.  The  growth  of  a 
plant  is  due  to  the  power  it  has  of  tearing  apart  the  carbon 
dioxide  by  the  help  of  the  sun  and  building  the  carbon 
into  its  structure.  It  returns  the  oxygen  to  the  air  to  be 
used  again  by  the  animals  and  plants. 

Experiment  69.  —  Get  two  or  three  bottles  of  carbon  dioxide  from 
the  chemical  laboratory,  or  prepare  it  by  pouring  dilute  hydrochloric 
acid  upon  pieces  of  limestone  in  a  bottle  and  collecting  the  gas  over 
water.  Does  the  appearance  of  this  gas  differ  in  any  way  from  that 
of  air?  Smell  of  one  of  the  bottles  that  has  stood  over  water  for 
some  time.  The  gas  has  no  odor.  Plunge  a  lighted  match  into  one 
of  the  bottles  containing  the  carbon  dioxide.  What  happens?  Does 
the  gas  burn  or  support  combustion?  Slowly  overturn  a  bottle  of 
the  gas  above  a  lighted  candle.  The  candle  is  extinguished.  The 
gas  falls  out  when  the  bottle  is  overturned,  thus  showing  that  it  is 
heavier  than  air.  If  the  amount  of  carbon  dioxide  in  the  air  were 
largely  increased,  what  effect  would  it  have  upon  combustion  ? 


114  FIRST  YEAR   SCIENCE 

Animals  smother  in  carbon  dioxide.  It  is  known  to 
coal  miners  as  choke  damp,  because  frequently  after  they 
have  escaped  from  an  explosion  they  are' smothered  by  it. 
It  occurs  at  a  few  localities,  as  at  the  Dog  Grotto  near 
Naples  and  in  Death  Gulch,  Yellowstone  National  Park, 
in  sufficient  quantities  to  be  fatal  to  animals  passing 
through  these  places. 

As  a  rule,  however,  the  proportion  of  oxygen,  nitrogen 
and  carbon  dioxide  is  the  same  for  all  places  on  the  sur- 
face of  the  earth  and  it  is  only  where  for  some  peculiar 
cause  carbon  dioxide  is  emitted  from  the  ground  in  a 
place  sheltered  from  the  wind,  that  it  can  accumulate.  As 
animals  and  men  breathe  it  out,  rooms  where  they  stay 
must  have  proper  ventilation. 

The  nitrogen  is  needed  to  dilute  the  oxygen.  If  oxygen 
were  undiluted,  animals  could  not  live,  and  a  fire  once 
started  would  burn  up  iron  as  readily  as  it  now  does  wood. 
As  has  already  been  stated,  certain  bacteria  take  nitrogen 
from  the  air  and  prepare  it  so  that  plants  can  use  it. 

Plants  and  animals  both  need  water  vapor.  Were  it 
not  for  this  form  of  moisture  there  would  be  no  rain,  and 
without  rain  life  could  not  exist.  Thus  the  air  which 
contains  oxygen  and  water  vapor  for  both  plants  and  an- 
imals, carbon  dioxide  for  the  plants,  and  nitrogen  to  dilute 
the  oxygen,  .is  one  of  the  greatest  factors  in 
the  life  history  of  the  earth. 

52.    Weight  of  Air.  —  Experiment  60.  —  Into   a  five- 
pint  bottle  insert  a  tightly  fitting  rubber  stopper  through 
which   a  glass  tube  extends.     To  the  outer  end  of  the 
glass  tube  tightly  fit  a  thick-walled  rubber  tube  of  suf- 
ficient length  for  the  attachment  of  an  air  pump.     Put 
Fig.  51.      a  Hoffman's  screw  upon  the  rubber  tube.     See  that  all 
connections  are  air-tight.     Weigh  carefully  the  apparatus 
as  thus   arranged.     Now   attach  the  rubber  tube   to  the  air-pump 
and  extract  the  air  from  the  bottle.     When  all  the  air  that  can  be 


EXPANSION   OF  AIR 


115 


exhausted  has  been  removed,  close  the  rubber  tube  tightly  with  the 
Hoffman's  screw  and  weigh  again.  Unclamp  the  Hoffman's  screw 
and  allow  the  air  to  enter  the  bottle.  The  weight  should  be  now  the 
same  as  at  first.  Or,  instead  of  weighing  a  bottle  of  air,  weigh  an 
incandescent  light  bulb.  Make  a  hole  in  it  with  a  blowpipe  and 
weigh  again.  Is  the  weight  now  the  same  as  before  ? 

We  have  found  by  the  previous  experiment  that  air  has 
weight.     With  the  apparatus  used  it  was  impossible  to 
tell  exactly  the  weight  of  the  air  extracted  or  to  determine 
the  weight  of  a  definite  volume  of 
the  air.     If  we  had  been  able  to  do 
this,  we  should  have  found  that  on 
an   average  day,   at  sea  level,  the 
weight  of  a  liter,  a  little  more  than 
a  quart,  of  air,  is  about  1.2  grams. 
12  cu.  ft.  weigh  about  1  Ib.     The 
air   extends   to   so   great   a  height 
that  although  very  light,  the  weight 
of  so  great  a  mass  of  it  is  consider- 
able. 

Now  that  air  has  been  found  to 
have  weight,  it  can  be  seen  why  a 
light  body  like  a  balloon  will  float 
in  it  in  the  same  way  that  a  stick 
will  float  in  water.  The  weight  of 

the  air  varies  with  the  pressure  and  temperature,  as  we 
shall  find  later. 

53.  Expansion  of  Air  when  Heated.  —  Air  expands  very 
much  when  heated,  as  was  seen  in  Experiment  17.  It  is 
found  that  if  air  at  freezing  is  heated  to  the  temperature 
of  boiling  water,  it  will  expand  about  -^  of  its  volume. 
The  force  with  which  air  expands  is  so  great  that  some- 
times when  buildings  are  on  fire  and  there  is  no  opening 
for  the  confined  air  to  escape,  the  walls  are  blown  out  or 


BALLOON. 

The  gas  in  the  halloon 
is  lighter  than  air,  so 
the  balloon  floats  in  air 
as  a  piece  of  wood  does 
in  water. 


116  FIRST   TEAR  SCIENCE 

jit 

the  roof  blown  off  by  the  expansion  of  the  hot  air,  and 
great  injury  done  to  those  fighting  the  fire.  That  air  ex- 
pands upon  being  heated  is  readily  seen  wjjen  a  toy  balloon 
is  brought  from  the  cold  outer  air  into  a  hot  room,  —  the 
covering  begins  at  once  to  tighten  and  the  balloon  to  swell. 

54.  Weight  of  Air  as  Affected  by  Heat  and  Cold.  —  Experi- 
ment 61.  —  Take  two  open  flasks  of  nearly  the  same  weight  and 
capacity  and  balance  in  as  nearly  a  vertical  position  as  possible  at  the 

ends  of  the  arms  of  a  beam  balance. 
Bring  the  flame  of  a  Bunsen  burner 
to  the  upper  side  of  the  bulb  of  one 
of  the  flasks  so  that  the  hot  air  cur- 
rents that  are  generated  will  have  no 
upward  push  on  the  flask.  Do  not 
allow  the  hot  air  to  get  under  the 
Fig.  52.  flask.  What  is  the  effect? 

As  the  previous  experiment  shows,  and  as  we  should 
expect  from  the  fact  that  air  has  been  found  to  expand 
when  heated,  it  follows  that  hot  air  is  lighter  than  cold 
air.  A  liter  of  air  at  freezing  under  ordinary  pressure 
weighs  about  1.293  grams,  but  at  the  temperature  of  boil- 
ing water  it  weighs  only  about  .946  grams.  So  a  mass  of 
cold  air,  being  heavier,  will  exert  more  pressure  at  the 
surface  of  the  earth  than  a  mass  of  hot  air. 

As  air  is  a  gas  whose  particles  can  move  freely  among 
themselves  we  should  expect  that  a  heavier  column  of  cold 
air  would  sink  down  and  distribute  itself  along  the  surface 
under  surrounding  lighter  air  just  as  a  column  of  water 
falls  when  its  supports  are  withdrawn  and  forces  up  the 
lighter  air  which  surrounds  it. 

A  similar  action  is  seen  when  water  is  poured  upon  oil; 
the  water  sinks  to  the  bottom  and  forces  the  oil  to  rise. 
Thus  if  air  is  heated  at  any  place,  we  should  expect  that 
there  would  be  a  rising  current  of  hot  air  and  a  current 


PRESSURE  OF  AIR 


117 


of  colder  air  creeping  in  to  take  its  place.  The  winds  of 
the  earth  are  due  to  this  property  of  air.  It  is  this  tend- 
ency of  heated  air  to 
rise  that  makes  hot  air 
furnaces  useful  for  heat- 
ing houses.  Valleys 
are  generally  colder 
than  the  surrounding 
hillsides,  so  that  deli- 
cate crops  can  be  grown 
successfully  on  the  hill- 
sides although  those  in 
the  valley  are  frost 
bitten. 


55.   Pressure  of  Air.  — 

Experiment  62.  —  Use  a  con- 
vection apparatus  or  take  a 
tight  chalk  box  and  in  two 
places  on  the  top  punch 
holes  in  a  circle  not  quite 


HOT  AIR  FURNACE. 

The  hot  air  rises  through  theipipes  and  regis- 
ters, and  cold  air  presses  in  from  outside. 


as  large  as  the  bottom  of  a  lamp  chimney.  Place 
a  small  lighted  candle  at  the  center  of  one  of  the 
circles  of  holes  and  a  lamp  chimney,  tightly  sealed 
to  the  box,  about  each  circle.  Hold  a  smoking 
piece  of  paper  above  the  chimney  which  does  not 
inclose  the  candle.  (If  a  pane  of  glass  is  put  into 
one  of  the  vertical  sides  of  the  box,  better  observa- 
tions can  be  made.)  What  happens  ?  Put  out  the 
candle  and  carefully  heat  the  chimney  with  a 

Bunsen   burner.     Is  there  the  same  action  as  be- 
Fig.  53.  fore?      Why   ig   it  that  sparkg   rise  from    a  fire? 

What  is  meant  by  the  draft  of  a  stove?    Why  in  order  to  ventilate 
a  room  is  it  best  to  open  a  window  at  the  top  and  bottom? 

Experiment  63.  —  If  a  tin  can  with  a  tightly  fitting  screw  cap  can 
be  easily  procured,  boil  a  little  water  in  it,  having  the  screw  cap  open 
so  that  the  steam  can  readily  escape.  While  the  water  is  still  strongly 
boiling,  quickly  remove  from  the  heat  and  tightly  cork.  Be  sure  not 


118  FIRST  YEAR   SCIENCE 

'  '        .  V* 

to  cork  before  removing  entirely  from  the  heat.  Set  the  tin  thus 
corked  upon  the  desk  and  observe.  What  happens  as  the  steam  con- 
denses? Why? 

Experiment  64.  —  By  means  of  an  air  pump  exhaust  the  air  from 
a  pair  of  Magdeburg  hemispheres.     Now  try  to  pull  the  hemispheres 

apart.     It  cannot  be   done  as  easily  as 
before  the  air  was  exhausted.     Why? 


Experiment  65.  —  Fill  a  glass  tumbler 
PJ      24  even  f^l  °f  water  and  press  upon  it  a 

piece  of  writing  paper.  Be  sure  that 
the  paper  fits  smoothly  to  the  rim  of  the  tumbler. 
Take  the  tumbler  by  its  base  and  carefully  invert 
it  over  a  pan.  Does  the  water  fall  out  ?  If  not,  why 
not?  While  the  tumbler  is  in  the  inverted  posi- 
tion, insert  the  point  of  a  pencil  between  the 
paper  and  the  rim  of  the  tumbler.  What  happens?  Fig.  55. 

Anything  that  has  weight  must  exert  pressure  upon  the 
surface  upon  which  it  rests.  The  air  has  been  founc^  to 
have  weight,  therefore  it  must  exert  pressure  at  the  sur- 
face of  the  earth.  Air  is  a  gas  and  its  particles  easily 
move  over  each  other,  therefore  this  pressure -is  exerted 
equally  in  all  directions.  No  one  feels  the  pressure,  how- 
ever, because  the  air  is  within  us  as  well  as  about  us. 
Those  that  have  measured  this  pressure  find  that  it  is 
about  fifteen  pounds  to  the  square  inch  at  sea  level.  If 
two  egg  shells  from  which  the  insides  had  been  removed, 
one  of  them  with  the  holes  left  in  it  and  the  other  com- 
pletely sealed,  were  sunk  to  a  considerable  depth  in  water, 
which  one  would  be  crushed  and  which  one  would  not  ? 
This  illustrates  why  we  are  not  crushed  by  the  pressure 
of  the  air  upon  us. 

56.  Decrease  of  Volume  due  to  Pressure.  —  Experiment  66.— 

In  a  Mariotte's  tube  cause  about  a  centimeter  of  mercury  in  the  short 
arm  to  balance  the  same  amount  in  the  long  arm.  The  pressure 
inside  the  short  tube  will  then  be  equal  to  that  outside  the  long  tube 


BAROMETERS  119 

and  will  be  that  of  the  air  upon  the  day  of  the  experiment.     The 
short  arm  will  now  be  sealed  with  mercury  so  that  no  air  can  get  in 
or  out.     Pour  mercury  into  the  long  arm.     The  air  in  the 
short  arm  will  be  gradually  compressed  and  .will  occupy 
less  and  less  space.     If  we  remember  that  the  pressure 
upon  the  air  in  the  short  arm  is  the  air  pressure  of  the 
day  plus  the  height  that  the  mercury  column  in  the  long 
arm  exceeds  that  in  the  short  arm,  we  can  show  by  care- 
ful measurement  that  the  volume  of  the  air  decreases  just 
as  the  pressure  increases. 

As  was  seen  in  Experiment  1,  the  volume  of 
the  air  can  be  very  much  decreased  by  pressure, 
but  when  the  pressure  is  removed,  it  regains  its 
original  volume.  It  cannot  be  told  from  this 
experiment  whether  the  volume  of  the  gas  de- 
creases as  the  pressure  increases  or  whether  it 
decreases  much  more  rapidly  when  first  pressed 
upon  than  afterward.  This  can  be  best  shown  by  the  use 
of  the  Mariotte's  tube  as  in  Experiment  66.  But  if  the 
bicycle  pump  is  a  good  one,  it  will  answer  the  question  of 
the  rate  of  decrease  quite  accurately.  It  is  found  that  the 
volume  decreases  directly  as  the  pressure  increases.  • 

57,  Barometers.  —  As  the  measurement  of  the  atmos- 
pheric pressure  is  of  great  importance  in  the  study  of 
atmospheric  conditions,  it  is  necessary  to  have  an  instru- 
ment by  which  these  measurements  can  be  readily  made. 
An  instrument  designed  for  this  purpose  is 
called  a  barometer.  There  are  two  kinds  of 
barometers  in  common  use,  called  the  mer- 
curial and  the  aneroid. 

Experiment     67.  —  (Teacher's    Exp.)     Take    a 
P.      27  thick-walled  glass  tube  of  about  £  cm.  bore  and 

about  90  cm.  long  and  slip  tightly  over  the  end  of 
it  about  10  cm.  of  a  thick-walled  flexible  rubber  tube  30  cm.  in  length. 
Firmly  secure  the  rubber  tube  to  the  glass  tube  by  winding  tightly 
around  them  many  turns  of  string,  making  it  impossible  for  the  rubber 


120 


.FIRST   YEAR   SCIENCE 


Fig.  58. 


I 


tube  to  slip  or  admit  air.  Completely  close  the  rubber  tube  with  a 
Hoffman's  screw  just  beyond  the  place  where  it  leaves  the  glass  tube. 
Placing  this  closed  end  in  a  large  dish  so  as  not  to  waste  any 
mercury,  fill  the  glass  tube  with  mercury.  Place  the  thumb 
over  the  open  end  of  the  tube  and  invert  it  in  a  cup  of  mer- 
cury. If  the  connections  were  made  tight,  the  mercury  will 
not  fall  far  below  the  end  of  the  glass  tube.  The  air  pres- 
sure keeps  the  mercury  up.  This  is  a  simple  form  of 
barometer. 

While  the  tube  is  still  standing  in  the  mercury  cup  take 
another  glass  tube  similar  to  the  first  and  attach  it  to  the 
open  end  of  the  rubber  tube  in  the  same  way  as  the  first  was 
attached.  Place  the  free  end  of  this  tube  in  a  dish  of  colored 
water  and  gradually  open  the  Hoffman's  screw.  The  water 
rises  in  the  tube.  Why?  What  is  meant  by  sucking  water 
up  a  tube  ? 

Experiment  68.  —  Fill  a  bottle  with  clean  water  and  fit  it 
tightly  with  a  rubber  stopper  having  two  holes  in  it.  Plug 
one  of  the  holes  tightly  with  a  glass  tube  one 
end  of  which  has  been  closed  by  heating  in  a 
Bunsen  burner.  Through  the  other  hole  put 
an  open  glass  tube  10  to  15  cm.  long.  See 
that  both  tubes  fit  tightly  in  the  stopper  and 
that  the  stopper  fits  tightly  in  the  bottle. 
Now  attempt  to  "  suck  "  the  water  out  of  the 
bottle  through  the  open  tube.  Does  it  come 
out  freely?  Pull  out  the  glass  plug.  Does 
it  come  out  any  better?  If  so,  why? 

The  mercurial  barometer  we  have  already  made 
in  a  rough  form.  The  best  form  of  these  instru- 
ments consists  of  a  glass  tube  of  uniform  bore 
about  eighty  centimeters  long  and  closed  at  one 
end.  After  being  carefully  filled  with  pure  mer- 
cury, it  is  inverted  in  a  cistern  of  mercury.  The 
cistern  of  mercury  has  a  sliding  bottom  easily 
moved  up  and  down  by  means  of  a  set  screw.  At 
the  top  of  the  cistern  there  is  a  short  ivory  peg.  g' 
The  lower  end  of  the  ivory  peg  is  at  an  exactly  measured 


DETERMINATION   OF  HEIGHT 


121 


distance  from  the  bottom  of  a  scale.     The  scale  is  placed 
beside  a  slit  near  the  top  of  a  metallic  tube  which  is  firmly 
fastened  to  the  cistern 
and  surrounds  and  pro- 
tects the  glass  tube. 

When  it  is  desired  to 
read  the  barometer,  the 
sliding  bottom  of  the 
cistern  is  raised  or  low- 
ered until  the  top  of  the 
mercury  in  the  cistern 
just  touches  the  bottom 
of  the  ivory  peg.  The 
height  of  the  top  of  the 
mercury  column  is  then 


read  from  the  scale.     In 


Fig.  60. 


order  to  determine  the  height  with  great  precision  there 
is  generally  attached  to  the  metallic  tube  a  sliding  vernier 

which  moves  in  the  slit. 
The  aneroid  barome- 
ter consists  in  general 
of  a  corrugated  metallic 
box  from  which  the  air 
has  been  partially  ex- 
hausted. Within  the 
box  is  a  stiff  spring  so 
that  the  pressure  of  the 
air  will  not  cause  it  to 
collapse.  Attached  to 
the  box  are  levers  by 
which  any  change  in  the 
volume  of  the  box  will  be  multiplied  and  indicated  by  a 
pointer  arranged  to  move  over  a  dial.  The  dial  has  a 
scale  upon  it  and  thus  the  air  pressure  is  registered. 


BAROGRAPH. 

This  is  arranged  so  as  to  record  the 
air  pressure  automatically  for  a  week 
at  a  time. 


122  FIRST   YEAR   SCIENCE 

Instruments  called  barographs  are  constructed  in  which 
a  long  lever  provided  with  a  pen  point  is  attached  to  the 
aneroid  and  made  to  record  on  a  cylinder  revolved  by 
clockwork.  Thus  a  continual  record  is  made  of  baro- 
metric readings. 

58.  Determination  of  Height  by  a  Barometer.— Experi- 
ment 69.  —  Carry  an  aneroid  barometer  from  the  bottom  of  a  high 
building  to  the  top.  Note  the  reading  of  the  barometer  at  the  bottom 
and  again  at  the  top.  Why  is  the  barometer  lower  at  the  top  of  the 
building  ? 

As  the  pressure  of  air  at  any  surface  is  due  to  the 
weight  of  the  air  above  that  surface,  it  happens  that  as  we 
go  up  the  pressure  decreases,  since  there  is  a  continually 
decreasing  weight  of  air  above.  If  the  rate  of  this  de- 
crease is  determined,  then  it  is  possible  to  determine  the 
elevation  by  ascertaining  the  pressure. 

Although  the  height  of  the  barometer  is  continually 
varying  with  the  changing  air  conditions,  yet  if  these  con- 
ditions remain  about  the  same,  it  may  roughly  be  esti- 
mated that  the  fall  of  -j1^  of  an  inch  in  the  height  of  the 
mercury  column  indicates  a  rise  of  about  57  feet,  and  that 
the  fall  of  a  millimeter  indicates  a  rise  of  about  11  meters. 
These  values  are  fairly  reliable  for  elevations  less  than  a 
thousand  feet,  under  ordinary  temperatures  and  pressures. 

At  the  height  of  25  miles  the  barometric  column  would 
probably  not  be  more  than  ^  of  an  inch  high.  Several 
measurements  made  in  different  ways  indicate  that  the  air 
is  at  least  100  miles  in  depth,  probably  more.  Nearly 
three  fourths  of  the  atmosphere  however  is  below  the  top 
of  the  highest  mountain.  The  highest  altitude  ever 
reached  by  man  was  about  7  miles. 

To  study  air  conditions  small  balloons  to  which  meteoro- 
logical instruments  are  attached  have  been  se'nt  to  a  height 
of  21  miles.  It  is  found  that  the  minimum  temperatures 


ADIABATIC  HEATING  123 

occur  at  a  height  of  from  6  to  10  miles.  Conditions  affect- 
ing weather,  however,  seem  to  extend  to  a  height  of  not 
much  over  3  miles. 

59.  Adiabatic  Heating  and  Cooling  of  Air.  —  Experiment  70. — 
Have  a  five-pint  glass  bottle  fitted  with  a  two-hole  rubber  stopper. 
Pass  through  the  holes  in  the  stopper  a  chemical  or  air 
thermometer  and  a  short  glass  tube  the  lower  end  of 
which  extends  into  the  bottle  not  near  the  bulb  of  the  ther- 
mometer, so  that  when  the  air  is  exhausted  or  allowed  to 
enter  the  bottle  there  will  be  no  movement  of  the  air 
near  the  bulb  of  the  thermometer.  The  end  of  the  column 
of  the  thermometer  must  be  visible  above  the  stopper. 

Attach  the  glass  tube  to  an  air  pump  by  means  of  a 
thick-walled  rubber  tube.  Note  the  temperature  of  the 
thermometer  within  the  bottle  and  also  of  the  air  outside.  &* 

Quickly  exhaust  the  air  from  the  bottle,  carefully  noting  the  action 
of  the  thermometer.  See  that  the  temperature  of  the  air  in  the  room 
does  not  change  during  the  experiment.  Allow  the  air  quickly  to 
enter  the  bottle  and  note  the  action  of  the  thermometer.  The  tem- 
perature inside  the  bottle  changes  as  the  air  is  quickly  exhausted,  or 
as  it  is  allowed  to  enter  the  bottle  again  and  thus  to  increase  the 
density  of  the  air  in  the  bottle. 

It  has  been  found  that  when  air  expands  its  temperature 
falls  and  when  it  is  compressed  its  temperature  rises.  This 
heating  and  cooling  of  the  air  without  the  application  of 
external  heat  or  cold,  but  simply  by  a  change  in  the  den- 
sity of  the  gas  itself,  is  called  adiabatic  heating  or  cooling. 
It  is  taken  advantage  of  in  the  manufacture  of  liquid  air 
and  is  the  same  principle  which  is  utilized  in  cold  storage 
plants.  This  property  of  air  has  much  to  do  in  develop- 
ing our  wind  circulation  and  storms. 

The  heating  effect  of  compressing  air  can  be  well  seen 
when  a  pneumatic  tire  is  filled.  No  matter  how  well  the 
piston  of  the  pump  may  be  oiled,  as  the  density  of  the  air 
in  the  tire  begins  to  increase,  the  pump  will  grow  warm 
rapidly.  This  rapid  heating  cannot  be  due  to  friction,  as 


124  FIRST   YEAR    SCIENCE 

the  pump  is  not  being  worked  any  more  swiftly  than  at 
first.  It  is  due  to  the  greater  compression  of  the  air.  As 
this  compression  increases,  the  heating  increases,  the  effect 
of  friction  in  a  well-oiled  pump  being  of  small  value. 

60.  Effect  of  Temperature  on  the  Capacity  of  the  Air  to  hold 
Moisture.  —  Experiment  71.  —  Take  a  liter  flask  and  put  into  it  just 
sufficient  water  to  make  a  thin  film  on  the  inside  of  the  flask  when 
shaken  around.  Now  warm  the  flask  gently,  never  bringing  its  tem- 
perature near  to  the  boiling  point,  until  the  water  disappears  from  the 
inside  and  the  flask  appears  to  be  perfectly  dry.  Having  tightly  corked 
the  flask,  allow  it  to  cool.  The  flask  appeared  dry  when  warm  and  on 
account  of  having  been  corked  tightly  no  moisture  could  have  entered 
it.  The  air" in  the  flask  was  perfectly  transparent  both  before  and 
after  heating.  The  film  of  water  around  the  inside  of  the  flask 
was  taken  up  by  the  air  when  it  was  warmed  but  the  moisture  re- 
appeared when  the  flask  was  cooled. 

Experiment  72.  —  Fill  a  bright  tin  dish  or  glass  beaker  with  ice  water 
and  after  carefully  wiping  the  outside  allow  it  to  stand  for  some  time 
in  a  warm  room.  Can  water  go  through  the  sides  of  the  dish  ?  Does 
the  outside  of  the  dish  remain  dry?  If  water  collects  upon  it,  from 
where  does  the  water  come  ?  See  if  the  same  results  will  happen  if  the 
water  within  the  dish  is  as  warm  as  or  warmer  than  the  air  in  the  room. 

Experiment  73.  —  Partially  fill  a  dish  or  beaker  like  that  in  the 
previous  experiment  with  water  having  a  temperature  a  little  warmer 
than  that  of  the  room.  Gradually  add  pieces  of  ice,  continually  stirring 
with  a  chemical  thermometer.  Note  the  temperature  at  which  a  mist 
begins  to  appear  upon  the  outside  of  the  dish.  When  the  mist  has 
appeared,  add  no  more  ice  but  stir  until  the  mist  begins  to  disappear. 
Note  this  temperature.  Take  the  average  of  these  wo  temperatures. 
This  average  is  probably  the  temperature  at  which  the  rnist  really 
began  to  form.  This  temperature  is  called  the  dew  point. 

When  we  wish  to  dry  clothes,  we  place  them  in  a  warm 
room  or  in  the  sunshine.  Soon  we  find  that  the  water  has 
left  the  clothes.  It  must  have  gone  into  the  air.  It 
would  thus  appear  that  when  the  temperature  of  the  air  is 
raised,  it  has  the  capacity  of  taking  up  more  moisture  than 
when  it  is  cold.  The  previous  experiment  has  shown  this, 


MOISTURE  IN  AIR  125 

and  the  one  in  which  the  dew  point  was  determined  showed 
that  when  heated  air  was  cooled  it  deposited  moisture. 

This  property  that  air  has  of  taking  up  a  large  amount 
of  water  when  heated  and  giving  it  out  when  cooled  is  the 
cause  of  our  clouds  and  rain.  If  it  were  not  for  this  there 
would  be  no  circulation  of  moisture  over  the  land,  no  rain, 
and  without  rain  there  could  be  no  vegetation  and  no 
animal  life.  Thus  this  simple  property  of  the  air  furnishes 
the  means  for  the  support  of  practically  all  the  animate  life 
on  the  earth. 

61.  Moisture  in  the  Atmosphere.  —  Experiment  74.  —  Carefully 
weigh  a  dish  of  water  and  place  it  in  a  convenient  place  where  there 
is  a  free  access  of  air.  After  some  hours  weigh  it  again.  What  causes 
the  change  of  weight?  Try  this  experiment  with  a  test  tube,  watch- 
glass  and  a  wide-mouthed  beaker  under  various  conditions  and  in 
various  places. 

The  atmosphere  at  all  times  and  under  all  conditions 
contains  some  moisture.  When  its  temperature  has  been 
raised,  its  capacity  to  hold  moisture  is  increased,  but  at 
no  place  is  it  so  cold  that  it  cannot  contain  a  certain 
amount  of  moisture.  When  water  in  the  solid  or  liquid 
condition  is  exposed  to  the  air,  it  gradually  disappears  and 
is  taken  up  into  the  air. 

If  the  water  surface  is  large  and  the  temperature  high, 
there  is  a  large  amount  of  evaporation  and  the  water 
rapidly  rises  into  the  air.  In  the  tropics  the  evaporation 
from  the  water  surface  amounts  to  perhaps  eight  feet  per 
year.  This  means  that  the  energy  of  the  sun  lifts  about 
five  hundred  pounds  of  water  from  every  square  foot  of  the 
surface  every  year.  In  the  polar  latitudes  the  amount  of 
evaporation  is  perhaps  a  tenth  of  that  in  the  tropics. 

From  every  water  surface  on  the  globe,  however,  a  large 
amount  of  water  is  evaporated  each  year.  In  many 
places  much  of  the  water  evaporated  falls  upon  the  same 


126 


FIRST   YEAR   SCIENCE 


surface  from  which  it  came,  but  a  considerable  part  of  it 
is  carried  by  the  winds  to  other  places  and  falls  upon  the 
land  surface,  furnishing  the  moisture  needed  for  the  land 
life  of  the  world. 

62.  Humidity.  —  The  condition  of  the  air  as  regards  the 
moisture  it  holds  is  called  its  humidity.  If  the  air  contains 
all  the  moisture  it  can  hold,  it  is  said  to  be  saturated  or  to 


CUMULUS  CLOUDS. 
Typical  low  level  clouds,  indicating  showers. 

have  reached  its  dew  point.  The  amount  of  vapor  present 
in  the  air  is  called  its  absolute  humidity.  The  amount  of 
vapor  in  the  air  divided  by  the  amount  that  it  would  con- 
tain if  it  were  saturated  is  called  the  relative  humidity. 
If  the  air  contains  much  moisture,  its  humidity  is  said  to 
be  high.  When  air  which  has  a  high  humidity  is  cooled, 
it  can  no  longer  hold  all  the  moisture  which  it  previously 
held,  and  this  moisture  will  be  deposited. 


ATMOSPHERE  AND  LIGHT  127 

The  moisture  in  the  air  may  form  into  little  droplets 
high  above  the  earth's  surface,  making  clouds,  or  these 
droplets  may  be  near  the  surface  of  the  earth.  In  this 
case  we  name  the  moisture  fog.  If  it  collects  on  objects 
attached  to  the  surface  we  call  it  dew. 


FOG. 
A  low  cloud  formed  near  the  surface  of  the  earth. 

By  determining  the  dew  point  as  was  done  in  Experi- 
ment 73  and  comparing  this  with  tables  which  have  been 
prepared  by  meteorologists  from  many  observations  the 
relative  humidity  can  be  readily  determined.  An  instru- 
ment for  determining  the  humidity  of  the  air  is  called  a 
hygrometer  (Fig.  62). 

63.  Effect  of  Atmospheric  Conditions  on  Light.  —  Experiment 
75.  —  Allow  sunlight  to  pass  through  a  glass  prism  and  fall  upon  a 
white  wall  or  piece  of  paper.  How  has  the  white  sunlight  been 
affected  ?  Where  did  the  colors  come  from  ?  In  what  order  are  the 
colors  arranged  ?  This  group  of  colors  into  which  a  prism  separates 
white  light  is  called  the  spectrum. 

If  the  light  that  comes  from  the  sun  is  passed  through  a 
glass  prism,  as  in  Experiment  75,  it  will  be  seen  to  be 


128 


FJRST   YEAR   SCIENCE 


composed  of  many  different  colors.  In  fact  it  is  the  ab- 
sorption of  some  of  these  colors  and  the  reflection  of 
others  which  make  objects  appear  of 
different  color. 

Light  itself  is  a  vibration  which  has 
the  power  of  affecting  the  optic  nerve, 
and  the  different  colors  are  vibrations 
of  different  lengths.  Now  the  sunlight 
is  affected  by  the  air  through  which  it 
comes.  If  there  is  smoke  or  dust  in 
the  air,  the  sun  will  appear  to  be  red. 
When  the  sun  sets  at  night  and  the 
rays  come  to  us  through  a  considerable 
thickness  of  air  which  is  near  the  sur- 
face of  the  earth  and  contains  dust,  the 
light  often  appears  red.  On  the  top 
of  a  high  mountain  or  on  a  clear  day  or 
when  the  sun  is  high  overhead  the  sky 
appears  blue.  Both  these  colors  are 
due  to  the  effect  of  the  atmosphere  on 
transmitted  light. 

Sometimes  after  a  shower  an  arch 
appears  in  the  heavens  composed  of 
beautiful  colors  ;  we  call  this  a  rain- 
bow. In  this  case  the  sunlight  is 
broken  into  its  different  colors  by  the 


Fig.  62. 


drops  of  water  or  little  ice  crystals  in  the  air,  just  as  it  is 
when  passing  through  a  prism. 

Sometimes  the  sun  or  moon  is  surrounded  by  bright 
rings  called,  when  of  small  diameter,  coronas,  and  when  of 
great  diameter,  halos.  These  rings  are  due  to  the  effect 
of  water  or  ice  particles  on  the  light  coming  from  the 
sun  or  the  moon. 

Under  certain  conditions  it  may  happen  that  light  com- 


ATMOSPHERE  AND  LIGHT  129 

ing  from  objects  at  a  distance  is  so  refracted  and  reflected  by 
the  layers  of  air  of  different  density,  through  which  it  comes 
to  the  eye  of  the  observer,  that  objects  appear  to  be  where 
they  are  not,  like  the  image  of  a  person  seen  in  a  mirror. 
This  phenomenon  is  called  mirage  or  looming.  It  occurs 
most  frequently  on  deserts  and  over  the  sea  near  the  coast. 
Sometimes  in  high  latitudes  arches  and  streamers  of 
colored  light  are  seen  illuminating  the  northern  sky.  The 


LICK  OBSERVATORY. 

As  light  is  affected  by  the  atmosphere,  observatories  must  be  placed 

where  atmospheric  conditions  are  the  best.    This  famous  observatory  is 

on  a  mountain  in  the  clear  air  of  California. 

brilliancy  and  colors  of  the  illumination  vary.  Sometimes 
it  is  bright  enough  to  be  seen  even  in  the  daytime.  This 
display  is  called  the  aurora  borealis  or  "  northern  lights  " 
and  is  believed  to  be  an  electrical  phenomenon  in  thin  air. 
The  heights  of  the  streamers  have  been  calculated  to  be 
more  than  a  hundred,  perhaps  several  hundred  miles,  so 
that  it  is  probable  that  air  in  a  rare  condition  extends  to 
this  elevation. 


130  FIRST   YEAR   SCIENCE 

A 

64.  The  Warming  of  the  Atmosphere.  —  The  sun  trans- 
mits both  light  and  heat  to  the  surface  of  the  earth 
through  the  atmosphere.  On  the  top  of  a  high  mountain 
the  temperature  is  found  to  be  colder  than  on  the  lower 
levels.  The  amount  of  sun  radiation,  technically  called 
insolation,  that  falls  upon  a  given  surface  on  the  mountain 
is  about  the  same  as  that  which  falls  upon  an  equal  sur- 
face in  the  valley.  If  the  heating  effect  is  less,  it  must 
be  due  to  something  besides  the  number  of  heat  rays  in- 
tercepted. 

In  the  spring  when  gardeners  wish  to  hurry  the  growth 
of  their  plants,  they  cover  them  with  boxes,  the  tops  of 

which  are  made  of  glass  (Fig. 
63).  It  is  found  that  the  tem- 
perature within  the  boxes  is 
higher  than  that  outside.  The 
heat  rays  coming  from  the  sun 

are  in  some  way  affected  by  the  reflection  of  the  ground  so 
that  they  are  not  able  to  get  out  through  the  glass  as 
readily  as  they  get  in. 

Now  the  atmosphere  affects  the  heat  rays  reflected  from 
the  earth  in  the  same  way  that  the  glass  does,  and  keeps 
them  from  flying  back  into  space  and  leaving  the  surface 
cold.  Where  the  atmosphere  is  thin,  as  on  the  moun- 
tains, this  effect  is  not  so  great,  and  therefore  the  surface 
is  colder  and  often  covered  with  snow.  When  there  are 
clouds  in  the  air,  they  help  to  hold  in  the  heat.  That  is 
why  in  the  fall,  when  it  is  getting  cold  enough  for  frosts, 
the  farmers  say  that  the  frosts  are  likely  to  come  on  clear 
nights  but  not  on  cloudy  ones. 

For  the  same  reason  plants  are  covered  by  pieces  of 
paper  and  smoky  fires  are  built  around  cranberry  bogs  to 
cover  them  with  an  artificial  cloud  of  smoke  on  nights 
when  there  is  likely  to  be  a  frost.  Thus  the  atmosphere 


ATMOSPHERIC   TEMPERATURES  131 

acts  as  a  blanket  to  the  earth  and  keeps  in  the  heat  of  the 
sun  just  as  blankets  on  a  bed  keep  in  the  heat  of  the  body. 
If  there  were  no  atmosphere  on  the  earth,  its  surface  would 
become  intensely  hot  during  the  day,  when  the  sun  shines 
directly  upon  it,  and  intensely  cold  at  night,  so  that  it 
would  not  be  possible  for  life  to  exist. 

It  has  been  estimated  that,  if  there  were  no  atmosphere, 
the  mean  temperature  of  the  earth's  surface  during  the 
day  would  be  350°  F.  and  daring  the  night  -  123°  F. 
Thus  the  atmosphere  is  not  only  needed  for  the  breathing 
of  plants  and  animals  and  for  carrying  moisture,  but  also 
for  keeping  in  the  heat  of  the  sun.  On  the  moon,  where 
there  is  no  atmosphere,  there  can  be  no  life  as  we  know  it. 

65.  Cause  of  the  Variation  in  Atmospheric  Temperatures.  — 
Experiment  76.  —  Cut  a  hole  4  in.  square  in  the  center  of  a  board  12 
in.  square.  Fit  tightly  into  this  hole  one  end  of  a  wooden  tube  4  in. 


Fig.  64. 

square  and  1  ft.  long.  Paint  the  inside  and  outside  of  the  tube  a  dull 
black.  Hinge  the  opposite  end  of  this  tube  10  in.  from  the  end  of  a 
baseboard  2  ft.  long  and  16  in.  wide,  having  6  in.  of  the  board  on 
either  side  of  the  tube. 

On  a  clear  day  place  this  apparatus  out  of  doors  on  a  table  freely 
exposed  to  the  sun  with  a  piece  of  paper  on  the  baseboard  under  the 
end  of  the  tube.  Point  the  tube  directly  at  the  sun  in  the  early 
morning,  in  the  middle  of  the  forenoon,  at  noon,  in  the  middle  of  the 
afternoon  and  about  sunset.  Mark  on  the  paper  the  amount  of  sur- 
face illuminated  by  the  sunlight  passing  through  the  tube  at  each  of 


132  FIRST   YEAR   SCIENCE 

--'».,  y* 

these  different  times.     Why  are  different  amounts  of  surface  covered 
at  these  different  times? 

Place  a  thermometer  in  the  centers  of  the  surfaces  covered  by  the 
sunlight  passing  through  the  tube  at  these  different  times.  Note  the 
different  readings  of  the  thermometer.  Can  you  suggest  a  reason  why 
they  are  not  alike?  The  opening  exposed  to  the  rays  has  been  the 
same  throughout  the  experiment.  Draw  diagrams  illustrating  the 
action  of  the  sun's  rays  in  the  different  positions. 

The  number  of  rays  of  the  sun  which  fall  upon  a  given 
area  depends  upon  the  angle  at  which  they  strike  the  sur- 
face. Figure  65  shows  that  the  same  number  of  rays  fall 


Fig.  65. 

upon  a  much  smaller  surface  when  the  direction  of  the  sun 
is  vertical  than  when  it  is  nearly  horizontal.  In  the  30- 
degree  arcs  there  are  2J,  7,  and  9|-  ray  spaces  respectively. 
The  sun  is  here  considered  to  be  vertical  at  the  equator, 
as  it  is  on  March  20  and  September  23.  Thus  on  these 
days,  other  conditions  being  the  same,  about  one  fourth 
as  much  heat  from  the  sun  falls  upon  the  30°  about  the 
pole  as  upon  the  30°  north  of  the  equator. 

The  latitude  of  a  place  has  much  to  do  with  the  amount 
of  heat  that  it  receives.     As  the  sun  becomes  vertical  to 


A  TMO  S  P HER  1C   TEMPERA  T  URES 


133 


places  north  of  the  equator,  the  length  of  the  day  in  the 
northern  hemisphere  increases  and  the  time  that  a  place  is 
in  the  sunshine  is  greater,  so  that  it  receives  more  heat 
from  the  sun.  On  the  21st  of  June  all  points  within 
23^°  of  the  north  pole, 
as  at  North  Cape,  have 
24  hours  of  sunshine, 
and  the  amount  of  heat 
received  at  the  pole  dur- 
ing these  24  hours  is 
greater  than  that  re- 
ceived at  the  equator 
where  the  day  is  only 
about  half  as  long. 

Although  the  latitude 
of  a  place  has  much  to 
do  with  the  amount  of 
heat  received,  there  are 
also  many  other  things 

which  affect  its  temperature.  This  will  appear  when  we 
consider  that  Venice,  Italy,  with  its  mild  and  equable 
climate  is  in  almost  the  same  latitude  as  Montreal,  Canada. 

As  has  been  seen,  the  height  above  the  sea  makes  a 
difference  with  the  temperature,  since  there  is  less  thick- 
ness of  air  above  and  therefore  a  thinner  blanket  to  hold 
the  heat.  Then,  too,  the  kind  of  soil  affects  the  tempera- 
ture. If  the  soil  is  sandy  and  there  is  little  or  no  veg- 
etation, it  becomes  rapidly  heated  in  the  daytime  and 
radiates  back  the  heat  into  the  air  very  rapidly,  thus 
making  the  temperature  of  the  air  near  the  surface  very 
hot  during  the  day ;  while  at  night,  when  the  sun  is  not 
adding  heat,  it  rapidly  loses  the  heat  acquired  during  the 
day,  and  so  the  temperature  of  the  air  becomes  low.  In 
the  daytime  on  great  sandy  deserts  the  heat  is  almost  un- 


A  WINTER  SCENE  IN  VENICE. 


134 


FIRST   YEAR   SCIENCE 


bearable,  but  at  night  it  is  so  cold  that  heavy  blankets  are 
needed  to  keep  the  traveler  warm. 

The  nearness  to  the  sea  and  the  direQtion  of  the  wind 
also  greatly  affect  the  temperature  of  a  place.  In  some 
parts  of  the  earth  these  are  the  principal  causes  in  de- 
termining the  temperature.  Thus  the  temperature  of  the 


A  WINTER  SCENE  IN  MONTREAL. 
The  famous  Ice  Palace,  built  entirely  of  blocks  of  ice. 

atmosphere  at  any  place  is  not  due  to  a  single  cause,  but 
is  the  result  of  many  and  complex  causes,  such  as  latitude, 
height,  direction  of  prevailing  winds,  ocean  currents,  near- 
ness to  the  sea,  and  kind  of  soil. 

Maps  are  sometimes  constructed  showing  heat  belts 
where  tropical,  temperate  and  frigid  conditions  are  found. 
These  belts  do  not  correspond  very  closely  to  the  torrid, 
temperate  and  frigid  latitude  zones. 

66.  Graphic  Method  of  Showing  the  Temperature  of  a 
Region.  —  It  is  often  quite  essential  that  the  temperature 


METHOD  OF  SHOWING  TEMPERATURES 


135 


over  a  considerable  region  should  be  known  and  a  record 

of  it  made  and  preserved.     This  might  be  done  by  taking 

a  map  and  writing  their 

temperatures  above  the 

different  places- marked 

on      the      map.      This 

would  make  a  map  full 

of    small    figures    and 

very  difficult  to  read. 

A  much  better 
method  has  been  devel- 
oped and  is  now  almost 


Notice  how  these  heat  belts  vary  from 
the  latitude  zones  shown  on  Figure  10, 
page  25. 


HEAT  BELTS. 

universally    used.       In 

making   this    map    the 

temperatures    are    first 

written  on  the  map  and  then  lines  are  drawn  through 

places  which  have  the  same  temperature.     These  lines  are 

called  isotherms  and  the  map  is  called  an  isothermal  map. 

By  the  use  of  such  a  map  it  is  possible  at  a  glance  to  de- 
termine the  temperature  prevail- 
ing at  any  place  and  to  see  the 
relation  which  this  has  to  the 
temperature  of  other  places  on 
the  map.  As  a  rule  the  isotherms 
are  not  drawn  for  each  degree, 
but  only  for  each  ten  degrees. 

When  the  map  has  been  con- 
structed, copies  are  made  in  which 
the  figures  are  left  off  and  only 
the  isotherms  are  preserved.  In 


Fig.  66. 


Figure  66  we  have  a  plan  before  the  isotherms  are  drawn, 
and  in  Figure  67  after  the  isotherms  are  drawn.  Figure 
68  is  a  typical  isothermal  diagram.  If  the  map  itself  were 
sketched,  it  would  be  an  isothermal  map. 


138 


•IRST   YEAR   SCIENCE 


Fig.  67. 


Maps  recording  barometric  conditions  are  made  in  the 

same  way  as  the  isothermal  maps,  only  their  lines  pass 

through  places  of  equal  baro- 
metric pressure  instead  of  places 
of  equal  temperature.  These 
lines  are  called  isobars. 

Weather  maps  are  prepared 
by  the  United  States  Weather 
Bureau  every  day,  on  which  are 
both  the  isotherms  and  isobars 
for  that  day.  The  data  for 
these  maps  are  telegraphed 
each  morning  from  stations 

scattered  all  over  the  settled  part  of  North  America. 
67.  Weather  Maps.  —  Expensive    weather    bureaus    are 

maintained  not  only  by  the  United  States,  but  by  all  the 

other  highly  civilized  countries 

of  the  world.     Records  are  kept 

also  by  sea  captains  and  by  other 

observers  throughout  the  world, 

and  these  are  gathered  together 

by  scientific  men  and  from  them 

are  made  charts  of  the  weather 

conditions  over  the  entire  surface 

of  the  earth.     Every  year  more 

and  more  data  are  being  collected 

and  these  charts  are  becoming  more  and  more  reliable. 
These  charts  are  of  great  value,  since  they  aid  in  the 

explanation  of  climatic  conditions  in  different  parts  of  the 

world.      The  results  of  the  data  thus  gathered  together 

have  been  of  untold  service  to  commerce  and  each  year 

have  saved  many  lives  and  a  vast  amount  of  wealth.     On 

pages  136  and  137  are  isothermal  maps  of  the  world  for  the 

months  of  January  and  July. 


AIR  PRESSURE  189 

68.  Land  and  Water  Temperatures.  —  As  was  seen  in  Ex- 
periment 27,  water  has  the  power  to  hold  a  great  amount 
of  heat.     During  the  summer,  water  is  heated  less  rapidly 
than  the  air  above  it,  so  it  continually  extracts  heat  from 
the  air,  making  the  air  cooler  than  it  otherwise  would  be. 
In  the  winter,  water  loses  its  heat  less  rapidly,  so,  being 
warmer  than  the  air  above  it,  it  constantly  gives  heat  to 
the  air.     Consequently  the  air  over  large  bodies  of  water 
changes  its  temperature  less  rapidly  than  does  the  air 
over  the  land. 

When  air  moves  in  wind  from  the  ocean  to  the  land,  it 
cools  the  land  in  summer  and  warms  it  in  winter.  It  is. 
found  therefore  that  lands  which  border  on  the  ocean 
usually  have  a  smaller  range  of  temperature  than  those 
which  are  far  from  the  sea.  On  some  islands  the  range 
of  temperature  throughout  the  year  is  almost  impercep- 
tible, whereas  in  the  interiors  of  continents  the  average 
temperature  of  some  of  the  summer  months  is  more  than 
a  hundred  degrees  higher  than  that  of  some  of  the  winter 
months. 

69.  Distribution  of  Air  Pressure  over  the  Earth.  — An  exam- 
ination of  the  isobar  maps  for  January  and  July  (pages  140 
and  141)  shows  that  atmospheric  pressure,  like  tempera- 
ture, is  greatly  affected  by  land  masses.     In  the  southern 
hemisphere,  south  of  40°  latitude  where  there  is  little  land, 
the  isobars  are  very  regular  in  their  directions  and  nearly 
parallel  to  the  parallels  of  latitude.     North  of  this  in  the 
same  hemisphere  they  are  somewhat  affected  -by  the  land, 
but  the  sea  is  still  the  predominant  influence. 

In  the  northern  hemisphere,  however,  the  land  and 
water  are  much  more  equally  divided  and  here  the  effect 
of  the  land  masses  is  at  once  apparent.  In  the  winter  the 
high-pressure  areas  and  the  low-temperature  areas  are 
found  over  the  land,  but  in  the  summer,  the  low-pressure 


w  to  w 

(0  W  (fl  « 

U  111  HI  111 

(E  K  C  K_ 

Q.  CL  0.  0.     - 


142 


FIRST   TEAR   SCIENCE 


areas  and  the  high-temperature  areas  are  over  the  land. 
This  illustrates  what  we  have  already  learned;  that  land 
heats  and  cools  much  more  rapidly  than  water  and  that 
hot  air  is  lighter  than  cold  air. 

In  both  summer  and  winter  there  is  an  area  of  compar- 
atively high  pressure  on  either  side  of  the  equator,  but  this 
area  is  not  fixed;  it  moves  north  and  south.  In  summer 
it  is  farthest  north  in  the'  northern  hemisphere. 

The  winds  are  simply  a  transfer  of  air  from  a  place 
where  the  pressure  is  high  to  a  place  where  it  is  low,  or  a 
transfer  of  air  along  what  are  called  barometric  gradients 
from  a  high  barometer  to  a  low  barometer.  So  the 
above-mentioned  changes  in  the  relation  between  the  pres- 
sure on  the  land  and  on  the  sea  must  have  an  effect  upon 
the  directions  of  the  winds.  As  a  rule  the  wind  blows  out 
from  the  land  interiors  in  the  winter  and  into  these  inte- 
riors in  the  summer.  It  is  thus  seen  that  isotherms  and 
isobars  are  closely  related  to  each  other,  and  that  the  wind 
is  but  a  result  of  the  atmospheric  conditions  which  they 
represent. 

70.  Wind.  —  Experiment  77.  —  On  a  (fay  when  the  temperature  in 
the  room  is  considerably  higher  than  that  outside,  open  a  window  at 
the  top  and  -bottom  and  hold  a  strip  of  tissue  paper  in  front  of  the 
opening.  Is  there  an  air  current,  and  if  so,  in  what  direction  does  it 

move  at  the  top  and  at  the  bottom  of 
the  window?  What  causes  "  drafts" 
in  a  room  ? 

Experiment  78.  —  Procure  two  sim- 
ilar dishes  about  15  cm.  high  and  5  or 
6  cm.  in  diameter  with  short  tubes 
of  about  1  cm.  in  diameter  opening 
Fig.  69.  out  from  near  the  top  and  bottom. 

Connect  the  bottom  tubes  of  the  two 

dishes  with  a  tightly  fitting  rubber  tube.  Do  the  same  with  the  top 
tubes.  Place  a  Hoffman's  screw  upon  each  of  the  rubber  tubes  and 
screw  it  tight  so  that  no  liquid  can  flow  through  either  tube.  Fill 


WIND  143 

one  of  the  dishes  with  colored  water  and  the  other  with  kerosene  or 
some  light  oil. 

Although  the  two  liquid  columns  are  similar,  yet  the  pressure  at 
the  bottom  of  the  dish  of  water  will  be  greater  than  that  at  the  bottom 
of  the  dish  of  oil  since  the  water  is  heavier  than  the  oil.  These  are 
the  conditions  that  exist  on  the  surface  of  the  earth  at  two  places  one 
of  which  has  a  high  and  the  other  a  low  barometer.  Release  the 
Hoffman's  screw  upon  the  top  tube  and  then  the  one  at  the  bottom. 
Notice  carefully  what  happens  as  the  lower  tube  is  allowed  to  open. 
The  dishes  are  not  now  filled  with  oil  and  water  respectively.  In  the 
transfer  of  the  liquids,  through  which  tube  did  each  pass  ?  (If  part 
of  each  rubber  tube  is  replaced  by  a  glass  tube,  the  action  in  the 
experiment  can  be  seen  to  better  advantage.) 

Experiment  79.  —  Fill  a  convection  apparatus  with  water,  putting  in 
a  little  sawdust  and  mixing  it  well  with  the  water.  Heat  one  side  of 
the  tube  and  observe  the  convection  currents  set  up. 

In  Experiment  78  the  interflow  from  one  dish 
to  the  other  is  due  to  the  fact  that  the  water  is 
heavier  than  the  oil  and  runs  under  it  and  pushes 
it  up  so  that  the  oil  overflows  into  the  dish  that' 
the  water  has  left.  The  same  thing  happens  in 
the  atmosphere  when  from  any  cause  the  column 
of  air  above  one  place  becomes  heavier  than  that 
above  another  place.  There  will  be  under  these 
conditions  a  transfer  of  air,  along  the  surface,  from  the 
place  where  the  pressure  is  greater  to  that  where  it  is  less 
great,  and  this  movement  of  the  air  we  call  wind. 

The  wind  on  the  surface  of  the  earth  is  not  usually  in 
the  same  direction  as  that  high  up.  The  strength  of  the 
wind  depends  upon  differences  in  air  pressures.  As 
the  air  pressure  is  measured  by  the  barometer,  the  wind 
is  commonly  spoken  of  as  due  to  a  difference  in  barometric 
pressure  or  to  the  barometric  gradient.  Winds  are  named 
from  the  direction  from  which  they  come.  A  west  wind 
is  a  wind  that  blows  from  the  west. 

If  there  were  no  other  forces  that  affected  the  movement 


144 


FIRST  TEAR   SCIENCE 


of  the  air,  except  the  high  and  low  pressures,  the  transfer 
would  be  in  a  straight  line  from  one  place  to  the  other, 
and  it  could  always  be  told  in  what  direction  the  high  and 
low  pressures  were,  by  direction  of  the  wind.  But  ob- 
stacles like  mountains  and  hills  deflect  the  air  currents. 
There  are  also  other  causes  which  influence  the  direction 
of  the  movement;  chief  among  these  is  the  rotation  of  the 
earth  on  its  axis. 

71.  Velocity  and  Effect  of  Wind  Action.— The  velocity  of 
air  movement  varies  from  a  gentle  breeze  which  has  not 

force  enough  to  stir  the 
leaves,  to  the  terrific  and 
almost  irresistible  blast 
of  the  tornado,  which 
sometimes  attains  a  ve- 
locity of  a  hundred  miles 
an  hour  and  sweeps 
everything  before  it. 
The  velocity  of  ordinary 
wind  is  measured  by  an 
instrument  called  an 
anemometer,  which  usu- 
ally consists  of  four 
aluminum  cups  attached 
by  horizontal  arms  to  a  vertical  spindle,  the  number  of 
revolutions  of  which  is  recorded  on  a  dial  by  a  train  of 
cogwheels  geared  to  the  spindle  (Fig.  71). 

When  the  wind  has  great  velocity,  it  can  be  estimated 
only  by  the  pressure  which  it  exerts.  A  measure  for 
the  velocity  of  wind  which  needs  no  apparatus  is  given 
by  Professor  Hazen  and  is  as  follows : 

0.  Calm. 

1.  Light ;  just  moving  the  leaves  of  trees. 

2.  Moderate ;  moving  branches. 


Fig.  71 


WIND  ACTION 


145 


3.  Brisk  ;  swaying  branches ;  blowing  up  dust. 

4.  High  ;  blowing  up  twigs  from  the  ground,  swaying 
whole  trees. 

5.  Gale  ;  breaking  small  branches,  loosening  bricks  on 
chimneys. 

6.  Hurricane,  or  tornado ;    destroying    everything   in 
its  path. 

Although  the  wind  in  its  great  paroxysms  of  rage  is 
sometimes  very  destructive,  it  is  ordinarily  a  most  benefi- 


A  DUTCH  WINDMILL. 
Windmills  are  widely  used  to  pump  water. 

cent  force.  It  is  the  circulatory  medium  for  the  earth  ;  as 
the  blood  is  for  the  animal  and  the  sap  for  the  plant.  With- 
out it  the  activities  of  the  earth  would  stagnate.  It  spreads 
over  the  land  the  water  evaporated  from  the  sea.  It  cools 
the  hot  regions  with  the  invigorating  breath  from  the 
mountains  and  the  uniformly  tempered  sea.  It  warms 
the  cold  places  by  bearing  to  them  the  heat  taken  from 
the  warm  ocean  waters  and  the  parched  places  of  the  earth. 


146 


FJRST   YEAR   SCIENCE 


It  bears  man's  commerce  across  the  seas  and  by  the  power 
of  the  water  which  it  has  borne  over  the  land,  furnishes 
him  the  means  for  his  manufacturing.  'It  scatters  the 
seeds  over  the  fields  and  sweeps  the  smoke  and  foul  air 
away  from  his  cities. 


EFFECT  OF  WIND  ON  THE  GROWTH  OF  TREES. 
The  trees  have  grown  in  the  direction  in  which  the  prevailing  wind  blows. 

72.  The  Effect  of  the  Earth's  Rotation  on  Winds.  —  Experi- 
ment 80.  —  Revolve  a  globe  from  left  to  right  and  while  it  is  revolv- 
ing draw  a  piece  of  chalk  from  the  pole  toward  the  equator.  Does 
the  line  as  marked  on  the  globe  follow  a  meridian  ?  What  is  its  gen- 
eral direction  in  lower  latitudes  ? 

The  rotation  of  the  earth  affects  the  direction  of  move- 
ment of  all  bodies  free  to  move  over  its  surface.  Thus  if 
a  current  of  air  starts  from  the  north  pole  to  flow  south,  it 
will,  as  it  goes  along,  tend  to  move  toward  the  right,  and  so 
when  it  reaches  middle  latitude  it  is  no  longer  moving 
south  but  southwest.  Why  this  is  so  can  be  fairly  well 


EFFECT  OF  EABTH'S  EOTATION 


147 


understood  if  the   conditions  of  this  moving  body  of  air 
are  considered. 

As  the  earth  is  about  25,000  miles  in  circumference  and 
turns  on  its  axis  once  in  24  hours,  a  body  situated  at  the 
equator  is  carried  from  west  to  east  at  the  rate  of  about 
1000  miles  per  hour,  whereas  a  body  at  the  poles  simply 


A  SAILING  VESSEL. 
Showing  how  the  wind  is  used  in  commerce. 

turns  around  during  a  revolution.  Thus  as  we  go  on  the 
surface  from  the  poles  toward  the  equator,  each  point  has 
an  increasing  west  to  east  velocity. 

A  body  of  air,  not  being  attached  to  the  surface,  will 
have  this  west  to  east  velocity  imparted  to  it  very  slowly 
by  friction.  Thus  as  it  goes  from  higher  to  lower  lati- 
tudes, it  will  lag  behind  particles  on  the  surface  which 
have  this  west  to  east  velocity,  and  so  will  appear  to  have 


148  FIRST   YEAR   SCIENCE 

'•*"*-•••  f* 

an  east  to  west  motion,  just  as  a  person  sitting  in  a  train 

that  is  just  starting  appears  to  be  sitting  still  and  the 
objects  outside  seem  to  move  in  the  opposite  direction. 
The  combination  of  the  north  to  south  movement  with 
the  apparent  east  to  west  movement  gives  a  northeast 
southwest  direction  to  the  air  current. 

It  can  be  proved  mathematically  that  all  freely  moving 
bodies  on  the  earth's  surface  are  deflected  toward  the  right 
in  the  northern  hemisphere  and  toward  the  left  in  the 
southern  hemisphere.  This  statement  is  called  Ferrel's  law. 

73.  Planetary  Wind  Belts.  — As  the  air  at  the  equator  re- 
ceives a  large  amount  of  heat,  it  becomes  warm  and  light, 
while  that  near  the  poles  is  cold  and  heavy.  The  air  would 
thus  have  a  constant  tendency  to  move  along  the  surface 
of  the  earth  toward  the  equator  and  in  an  upper  current 
from  the  equator  toward  the  poles,  just  as  in  the  dishes 
where  water  and  oil  were  connected.  But  this  direct 
movement  is  affected  by  the  rotation  of  the  earth  and  by 
certain  atmospheric  conditions  so  that  between  25°  and  35° 
both  north  and  south  of  the  equator  there  is  an  area  of 
high  pressure.  These  high-pressure  areas  can  be  seen  on 
the  isobar  maps  of  January  and  July. 

From  these  areas  of  high  pressure  the  surface  currents 
move  both  toward  the  equator  and  toward  the  poles.  On 
account  of  the  earth's  rotation  the  directions  of  these 
movements  are  not  north  and  south  but  in  the  northern 
hemisphere  northeast  and  southwest.  Winds  of  this  kind 
must  occur  on  every  revolving  planet  having  an  atmos- 
phere; hence  these  winds  are  called  planetary  winds. 

As  the  rotation  of  the  earth  and  the  heating  of  the  air 
near  the  equator  are  conditions  that  do  not  change,  among 
the  most  permanent  things  about  our  planet  are  the  belts 
into  which  the  wind  circulation  is  divided.  The  change 
in  the  position  of  the  heat  equator,  —  the  belt  of  highest 


WIND  BELTS   OF  THE  EARTH 


149 


temperature,  —  due  to  the  apparent  movement  of  the  sun 
north  and  southv  modifies  the  conditions  in  these  wind 
belts  during  the  year.  The  planetary  winds  thus  modified 
are  sometimes  called  terrestrial  winds. 

74.  Wind  Belts  of  the  Earth.  —  Near  the  heat  equator 
where  the  air  is  rising  there  is  a  belt  of  calms  and  light 
breezes  called  the  doldrums.  As  the  air  here  is  rising 
and  cooling,  thus  having  its  capacity  to  hold  moisture  de- 
creased, this  is  a  cloudy  rainy  belt  of  high  temperature  in 
which  much  of  the  land 
is  marshy  and  the  vege- 
tation so  rank  and  lux- 
uriant that  agriculture 
is  exceedingly  difficult. 

Extending  north  and 
south   of   the   doldrums 


WIND  BELTS  OF  THE  EA.RTH. 


to  about  28°  of  latitude 
are  belts  in  which  con- 
stant winds  blow  toward 
the  doldrum  belt  and 
supply  the  air  for  the 
upward  current  there. 
In  the  northern  hemi- 
sphere these  winds  have  a  northeast  to  southwest  direction 
and  in  the  southern  hemisphere  a  southeast  to  northwest 
direction.  They  are  the  most  constant  winds  on  the  globe 
in  their  intensity  and  direction,  and  are  called  trade  winds. 
Since  they  blow  from  a  cold  region  to  a  warmer  region,  their 
power  to  hold  moisture  is  constantly  increasing  and  clouds 
and  rains  are  not  usual.  The  places  where  they  blow  are 
dry  belts  and  in  them  are  found  the  great  dry  deserts  of 
the  world. 

On  the  poleward  sides  of  the  trade- wind  belts  lie  the 
areas  of  high  pressure  already  referred  to.     These  are 


152  FIRST   YEAR   SCIENCE 

'  .  ** 

called  the  horse  latitudes  or  belts  of  tropical  calms  and 
are  rather  ill-defined.  The  air  is  here  descending  and 
the  surface  movements  are  light  and  irregular.  These, 
like  the  doldrums,  are  regions  of  calms.  But  unlike  the 
doldrums,  they  are  dry  belts,  since  the  temperature  of  the 
descending  air  is  increasing,  owing  to  adiabatic  heating 
(§  59),  and  thus  its  power  to  hold  moisture  is  increasing. 
Therefore  the  tendency  in  these  belts  is  to  take  up  mois- 
ture rather  than  to  deposit  it. 

In  the  middle  latitudes  there  is  a  belt  of  irregular  winds 
which  have  a  prevailing  tendency  to  move  from  west  to  east 
or  northeast.  This  general  eastward  drift  of  the  air  is  con- 
stantly being  interrupted  by  great  rotary  air  movements  hav- 
ing a  diameter  of  from  500  to  1000  miles.  These  are  called 
cyclones  and  anti- cyclones.  In  this  region  of  the  "wester- 
lies," since  the  air  tends  to  move  from  lower  to  higher  latr 
itudes,  an  abundance  of  moisture  is  usually  supplied. 

In  the  anti-cyclone  the  air  movement  is  slowly  down- 
ward and  outward  from  the  center  and  in  the  cyclone  it 
is  inward  toward  the  center,  and  upward.  The  center  of 
the  anti-cyclone  is  a  place  of  clear  sky  and  high  pressure, 
while  that  of  the  cyclone  is  a  place  of  cloudy  sky  and  low 
pressure.  The  anti-cyclones,  or  high-pressure  areas,  have 
dry,  cold,  light  winds,  while  those  of  the  cyclones,  or  low- 
pressure  areas,  are  usually  strong  and  wet. 

75.  Land  and  Water  Winds.  —  As  the  land  is  much  more 
rapidly  heated  by  the  rays  of  the  sun  than  is  the  water, 
the  land  during  the  daytime  becomes  hotter  than  the 
water  near  it.  On  this  account  the  cool  air  over  the 
water  flows  in  over  the  land  and  displaces  the  lighter  warm 
air.  Therefore  near  large  bodies  of  water  when  the 
temperature  is  high  there  is  often  in  the  daytime  a  wind 
blowing  from  the  water  to  the  land.  At  night,  as  the  land 
loses  its  heat  more  rapidly  than  the  water,  the  wind  blows 


MONSOONS 


153 


in  the  opposite  direction.  These  water  winds  temper  the 
climate  of  the  tropics  near  the  coasts  and  also  render  sea- 
side resorts  popular  in  summer. 

76.  Monsoons.  —  Over  the  interior  of  the  great  continent 
of  Asia  the  temperature  becomes  so  high  in  the  summer 
months  that  the  air  above  it  is  greatly  expanded  and  de- 
creases in  weight.  This  causes  a  strong  indraft  from  the 
colder  ocean.  The  high  temperature  also  brings  the  heat 
equator  far  north  of  tho  earth's  equator  and  causes  the 


& 


^  V  ^  V  ^     f 


Fig.  72. 


Fig.  73. 


southeast  trade  winds  to  cross  the  earth's  equator.  These 
swing  to  the  right  on  the  north  side  of  the  equator  and 
proceed  as  southwest  winds  (Fig.  72),  thus  greatly 
strengthening  the  air  movement  toward  the  heated  conti- 
nental interior. 

The  winds,  being  heavily  loaded  with  moisture  from  their 
passage  over  the  tropical  seas,  are  forced  to  rise  when  they 
come  upon  the  high  lands  of  India  near  the  coast.  There 
they  become  cooled  and  deposit  a  great  amount  of  rain, 
making  this  southern  part  of  Asia  the  place  of  greatest 
rainfall  on  the  earth. 

In  the  winter,  when  the  heat  equator  has  moved  south 
and  when  the  continental  interior  has  become  exceedingly 
cold,  there  is  a  strong  movement  of  air  out  from  it  toward 
the  warmer  ocean  (Fig.  73).  This  strengthens  the  north- 


154  FIRST   YEAR   SCIENCE 

'    '  •  f* 

east  trade  winds  over  the  Indian  Ocean.  It  thus  happens 
that,  near  the  southern  coast  of  Asia  there  are  strong  sea- 
sonal winds  that  blow  toward  the  northeast  in  summer  and 
toward  the  southwest  in  winter.  These  winds  are  called 
monsoons.  In  the  early  sailing  voyages  to  India  they  were 
very  important,  the  trip  to  India  being  made  so  as  to  uti- 
lize the  summer  monsoons  and  that  from  India  so  as  to  uti- 
lize the  winter  monsoons.  On  this  account  these  winds 
had  much  to  do  with  the  conquest  of  India  by  the  nations 
of  Europe. 

77.  Rainfall  and  its  Measurement.  — Experiment  81.  —  Place  a 
dish  with  vertical  sides  in  a  large  open  space  so  that  the  rim  is 
horizontal  and  at  a  height  of  about  one  foot  above  the  ground. 
Fasten  the  dish  so  that  it  cannot  be  overturned  by  the  wind.  After 
a  rain,  measure  the  water  that  has  collected  in  the  dish  to  the 
smallest  fraction  of  an  inch  possible.  This  will  be  the  amount  of 
rainfall  for  this  storm. 

The  amount  of  rainfall  during  the  year  varies  greatly 
in  different  places.  It  amounts  to  nothing  or  only  a  few 
inches  over  some  regions,  as  in  parts  of  Peru  where  rain 
falls  only  on  an  average  of  once  in  five  years.  But  in  the 
Khasi  Hills  region  of  India  it  has  been  known  to  be  over 
600  inches ;  and  over  40  inches,  or  about  the  average 
yearly  rainfall  for  the  eastern  United  States,  has  been 
known  to  fall  in  24  hours.  This  was  in  the  season  of 
the  southwestern  monsoons. 

The  rainfall  in  different  parts  of  the  earth  has  been 
carefully  measured  and  maps  showing  its  average  amount 
prepared.  As  agriculture  is  largely  dependent  upon  the 
amount  of  rain  and  the  season  of  the  year  in  which  it 
falls,  these  maps  tell  much  about  the  relative  productivity 
of  different  regions  of  the  earth.  An  annual  total  of 
eighteen  or  more  inches  is  necessary  for  agriculture ;  and 
this  must  be  properly  distributed  throughout  the  year. 


356  FIRST   TEAR   SCIENCE 

"    '  i* 

On  examining  the  map  of  the  mean  annual  rainfall,  we 
see  that  there  are  large  areas  where  it  is  not  sufficient  for 
agriculture  without  irrigation.  Such  arefts  are  within  the 
belts  of  dry  winds  or  in  continental  interiors  far  from 
large  bodies  of  water.  The  rain-bearing  winds  coming 
from  the  water  are  forced  to  rise  and  cool  so  that  their 
moisture  is  deposited  before  reaching  these  interior  regions. 
The  rainfall  of  a  place  depends  largely :  (1)  upon  its 
elevation,  since  most  of  the  rain -bearing  clouds  lie  at  low 
altitudes ;  (2)  upon  the  direction  and  kind  of  winds  that 
blow  over  it ;  and  (3)  upon  the  elevation  of  the  land  about 
it.  The  sides  of  mountains  toward  the  direction  from 
which  the  rain-bearing  winds  approach  will  be  well 
watered,  while  the  opposite  side  may  be  a  dry  desert. 
Explain  the  cause  of  the  dryness  of  five  of  the  great  dry 
regions  as  found  on  the  map  on  page  155. 

A  cylindrical  vessel  having  vertical  sides,  called  a  rain 
gauge  (Fig.  74),  is  used  to  determine  the  amount  of  rain. 
It  is  placed  in  an  open  space  away  from  all  trees 
and  buildings  and  after  each  rain  the  amount  col- 
lected is  measured.  Snow  is  melted  before  it  is 
measured.  As  a  rule  eight  or  ten  inches  of  snow 
make  an  inch  of  rain. 

If  the  temperature  is  below  the  freezing  point, 
32°  F.,  when  condensation  takes  place,  the  mois- 
ture of  the  air  will  form  into  a  wonderful  variety 
of  beautiful  six-rayed  snowflakes.  These  float 
downward  through  the  air  and  often  cover  the 
ground  with  thick  layers  of  snow.  Although 
snow  is  itself  cold,  yet  it  keeps  in  the  heat  of  the  ground 
which  it  covers,  so  that  in  cold  regions  soil  which  is  snow- 
covered  does  not  freeze  as  deeply  as  that  without  snow. 
Therefore,  to  keep  water  pipes  from  freezing,  it  is  not 
necessary  to  bury  them  as  deeply  in  localities  where 


RAINFALL   OF  THE  UNITED   STATES 


157 


snow  is  abundant  as  in  places  equally  cold  where  snow 
seldom  falls. 

If  raindrops  become  frozen  into  little  balls  in  their 
passage  through  the  air,  they  fall  as  hail.  Hail  usually 
occurs  in  summer  and  is  probably  caused  by  ascending 
currents  of  air  carrying  the  raindrops  to  such  a  height 
that  they  are  frozen  and  often  mixed  with  snow  before 
they  fall.  Sometimes  hailstones  are  more  than  a  half  inch 
in  diameter.  They  occasionally  do  great  damage  to  crops 
and  to  the  glass  in  buildings. 

Sleet  is  a  mixture  of  snow  and  rain. 

78.  Rainfall  of  the  United  States.  — An  examination  of  a 
rainfall  map  of  the  United 
States  (page  158)  will 
show  that  the  distribution 
of  rainfall  can  readily  be 
divided  into  four  belts 
which,  although  gradually 
shading  the  one  into  the 
other,  are  yet  quite  dis- 
tinct. These  belts  may 
be  called  the  north  Pacific 
slope,  the  south  Pacific 
slope,  the  western  interior 
region,  and  the  eastern 
region. 

In  the  north  Pacific 
coast  region  the  storms 
of  the  "westerlies"  are 
common,  particularly  in 
winter,  when  the  westerly 
winds  are  strong  and  stormy.  The  yearly  rainfall  here 
amounts  to  about  seventy  inches. 

From  central  California  south  the  rainfall  of  the  Pacific 


SALMON  RIVER  DAM,  IDAHO. 

A  typical  irrigation  dam  in  the  United 

States. 


RAINFALL   OF  THE   UNITED   STATES 


159 


slope  decreases  until,  in  southern  California,  there  is  al- 
most no  rain  in  summer  and  the  entire  rainfall  for  the 
year  averages  about  15  inches.  By  reference  to  the  isobar 
map  of  the  world  (page  141)  it  will  be  seen  that  the 
high-pressure  area  of  the  dry  tropical  calm  belt  moves 
sufficiently  far  north  in  summer  to  take  this  region  out  of 
the  influence  of  the  wet  westerlies  and  into  that  of  the 
drier  belt. 

The  western  interior  region,  extending  from  the  Cas- 
cade and    Sierra  Nevada  mountains  to  about   the    100th 


EAST  END  OF  THE  ASSUAN  DAM  ACROSS  THE  NILE. 
The  greatest  irrigation  dam  in  the  world. 

meridian,  is  dr^y  over  the  larger  part  of  its  surface,  since 
the  winds  have  deposited  most  of  their  moisture  in  pass- 
ing over  the  mountains  to  the  west.  On  the  mountains 
and  high  plateaus,  however,  there  is  a  considerable  fall  of 
rain,  as  the  winds  are  cooled  sufficiently  in  passing  over 
these  to  deposit  their  remaining  moisture.  In  most  of 
this  region,  as  in  southern  California,  irrigation  must  be 


160  FIRST   YEAR   SCIENCE 

'  '  '  .  y* 

resorted  to  if  agriculture  is  to  succeed.  The  fall  of  rain 
on  the  mountains  and  high  plateaus  supplies  rivers  of 
sufficient  size  to  furnish  water  for  extensive  irrigation, 
and  so  a  considerable  part  of  the  area  which  is  now  prac- 
tically a  desert  will  in  the  future  be  reclaimed  for  the  use 
of  man.  The  government  is  at  present  engaged  in  ex- 
tensive irrigation  work  in  this  territory. 

From  about  the  100th  meridian  to  the  Atlantic  Ocean 
there  is  a  varying  rainfall,  but  it  is  as  a  rule  sufficient  for 
the  needs  of  agriculture.  It  gradually  increases  toward 
the  east,  moisture  being  supplied  plentifully  from  the  Gulf 
of  Mexico  and.  the  Atlantic  Ocean  by  the  southerly  and 
easterly  winds.  The  rainfall  is  well  distributed  through- 
out the  year  and  averages  from  thirty  to  sixty  inches. 

79.  Electricity.  —  Experiment  82. — Place  some  small  pieces  of 
paper  or  pith  balls  on  a  table  and  after  rubbing  a  glass  rod  with  silk 
bring  it  near  the  pieces.  Do  the  same  with  a  stick  of  sealing  wax  or 
a  hard-rubber  rod  rubbed  with  flannel  or  a  cat's  skin.  Note  the 
action  of  the  pieces. 

Experiment  83.  —  Rub  a  glass  rod  briskly  with  silk  and  place  in  a 
wire  sling  such  as  was  used  in  Experiment  12.  Bring  toward  one 
end  of  the  glass  rod  another  glass  rod  which  has  been  rubbed  with 
silk.  Do  the  rods  attract  or  repel  each  other?  Bring  toward  the 
suspended  rod  a  piece  of  sealing  wax  or  a  vulcanite  rod  which  has 
been  rubbed  with  flannel  or  a  cat's  skin.  Does  this  repel  or  attract 
the  glass  rod? 

Experiment  84.  —  Suspend  a  pith  ball  by  a  silk  thread  from  the 
ring  of  a  ring  stand.  Rub  a  glass  rod  with  a  piece  of  silk  and  bring 
it  near  the  pith  ball  but  do  not  allow  the  two  to  touch.  Note  the 
action  of  the  ball.  Touch  the  pith  ball  with  the  rod.  Does  it  behave 
now  as  it  did  before  ?  Rub  a  vulcanite  rod  with  a  piece  of  flannel  or 
cat's  skin  and  bring  it  near  a  suspended  pith  ball.  Does  the  pith  ball 
act  as  it  did  with  the  glass  rod  ?  Touch  the  pith  ball  with  the  rod. 
How  does  it  act  ?  Bring  a  glass  rod  rubbed  with  silk  near  a  pith  ball 
which  has  been  in  contact  with  a  vulcanite  rod  after  it  was  rubbed 
with  flannel  or  a  cat's  skin.  Does  the  glass  rod  repel  or  attract  the 
ball? 


ELECTRICITY  161 

Experiment  85.  —  Suspend  a  pith  ball  from  the  ring  of  a  ring  stand 
by  a  very  fine  piece  of  copper  wire  no  larger  than  a  thread.  Wrap 
the  wire  around  the  pith  ball  in  several  directions.  Bring  a  rubbed 
glass  rod  toward  the  pith  ball.  Does  it  act  as  it  did  when  suspended 
by  silk  ?  Allow  the  ball  to  touch  the  rod.  Does  the  ball  now  act  as 
it  did  when  suspended  by  silk?  Try  these  same  experiments,  using 
the  vulcanite  rod. 

It  was  known  by  the  ancient  Greeks  that  when  certain 
substances,  one  of  which  was  amber,  were  rubbed,  they 
had  the  power  of  attracting  light  objects.  This  property 
was  afterward  called  electricity,  from  the  Greek  word  for 
amber.  From  the  previous  experiments  it  has  been  seen 
that  when  glass  is  rubbed  with  silk,  and  vulcanite  with 
flannel  or  a  cat's  skin,  they  seem  to  have  two  different 
kinds  of  electrical  charges.  The  like  kinds  repel  each 
other  and  the  opposite  kinds  attract.  These  two  kinds 
are  called  positive  and  negative  respectively. 

Whether  there  are  really  two  kinds  of  electricity  has  not 
yet  been  fully  determined,  but  electricity  acts  exactly  as  it 
would  if  there  were  two  kinds,  and  it  has  become  customary 
to  speak  as  if  there  were.  In  Experiment  84  it  was  found 
that  pith  balls  suspended  by  a  silk  thread  could  be  charged 
with  electricity  if  brought  in  contact  with  a  charged  body. 
Experiment  85  showed  that  this  was  not  possible  when  they 
were  suspended  by  a  copper  wire.  The  wire  conducted 
the  electricity  away.  Substances  like  copper  that  conduct 
electricity  are  called  conductors,  and  those  substances  like 
silk  which  will  not  conduct  it,  nonconductors. 

Experiment  86.  —  Having  started  the  electrical  action  in  a  static 
electrical  machine  (Fig.  75),  pull  the  knobs  as  far  apart  as  the  spark 
will  jump  and  notice  the  course  taken  by  the  spark.  Does  it  travel  in 
a  straight  line  ?  Hold  a  piece  of  cardboard  between  the  knobs  so  that 
its  edge  is  just  within  the  line  joining  them.  What  effect  does  the 
cardboard  have  upon  the  direction  taken  by  the  spark?  Place  the 
cardboard  so  that  it  entirely  covers  one  of  the  knobs.  Is  the  spark 
able  to  pass  through  the  card?  Attach  a  wire  with  a  sharp  point 


162 


FIRST   YEAH   SCIENCE 


to  each  of  the  knobs  and  extend  it  vertically  two  or  three  inches  above 
the  knob.  Start  the  machine.  Do  sparks  now  jump  across  between 
the  knobs?  Why  are  houses  provided  with  lightlying  rods? 


Fig.  75. 

About  the  middle  of  the  eighteenth  century,  Benjamin 
Franklin   proved   by   his   notable   kite    experiment   that 

lightning  was  simply  an  elec- 
trical discharge  between  the 
clouds  and  the  earth,  or  be- 
tween different  clouds.  This 
discharge  is  similar  to  that 
which  takes  place  on  an  elec- 
trical machine.  The  electricity 
in  the  clouds  attracts  as  near  as 
possible  the  opposite  kind  of 
electricity  on  the  earth's  surface 
and  tends  to  hold  it  accumu- 
lated on  high  objects.  If  the  attraction  is  sufficient,  the 
electricity  discharges  between  the  cloud  and  the  object, 
and  we  say  the  object  was  struck  by  lightning. 


A  FLASH  OF  LIGHTNING. 

Showing  it  takes  different  paths 
of  least  resistance. 


THUNDER-STORMS 


163 


If  a  sharp  point,  such  as  a  lightning  rod,  is  present  on 
the  object  where  the  electricity  tends  to  accumulate,  it 

allows  the  electricity  to 

pass  off  gradually  before 
enough  accumulates  to 
cause  damage.  Light- 
ning rods,  however, 
must  be  continuous 
conductors  and  prop- 
erly terminated  in  the 
ground. 

80.  Thunder-storms.  - 
Often  on  a  hot,  sultry 
summer  afternoon  large 
cumulus  clouds  are  seen 
to  rise  and  spread  out 
till  they  cover  the  sky. 
The  wind  soon  begins 
to  blow  quite  strongly 
toward  the  cloud-covered  area,  the  clouds  moving  in  a 
direction  opposite  to  the  surface  wind.  As  the  storm 
clouds  approach,  a  violent  blast  of  wind,  often  called  the 
thunder  squall,  blows  out  from  the  front  of  the  storm. 
Soon  flashes  of  lightning  appear  and  thunder  is  heard. 
As  the  storm  comes  nearer,  the  rain  begins  to  descend 
and  for  a  short  time,  usually  about  half  an  hour,  it  rains 
heavily.  Then  the  clouds  roll  away  and  the  sky  becomes 
clear  with  perhaps  a  rainbow  to  heighten  the  beauty  of  the 
clearing  landscape. 

Thunder-storms  are  caused  by  hot  moist  air  rising  over 
certain  areas  and  causing  an  updraft,  which  is  increased 
by  the  inflow  and  upward,  movement  of  air  from  the  sur- 
rounding regions.  The  condensation  of  the  moisture  in  the 
rising  air  quickly  forms  clouds,  and  these  become  charged 


TREE  COMPLETELY  SHATTERED  BY  A 
STROKE  OF  LIGHTNING. 


164  FIRST   YEAR   SCIENCE 

*  .  .,«• 

with  electricity.  As  the  electrical  charge  increases,  dis- 
charges take  place  which  cause  lightning  flashes.  These 
discharges  occur  along  the  lines  of  least  resistance  and  are 
often  very  irregular  and  forked.  As  tall  objects  are 
likely,  to  offer  good  paths  for  the  discharge,  it  is  safest  to 
keep  away  from  trees  and  walls  during  a  thunder-storm. 

The  air  becomes  greatly  agitated  by  the  lightning  dis- 
charges and  makes  us  aware  of  this  by  the  noise  of  the 
thunder,  just  as  the  agitation  of  the  air  caused  by  the 


THUNDER-STORM  CLOUDS. 

discharge  of  a  gun  is  made  apparent  to  us  by  what  we  call 
the  noise  of  the  report.  Since  sound  travels  at  about  the 
rate  of  a  mile  in  five  seconds  and  the  lightning  discharge 
is  practically  instantaneous,  the  noise  from  different  parts 
of  the  discharge  will  reach  us  at  different  times  and  to 
this  and  the  echoing  from  clouds  or  hills  is  due  the  roll  of 
the  thunder.  The  distance  of*  the  flash  can  be  told  ap- 
proximately by  dividing  the  number  of  seconds  between 
seeing  the  flash  and  hearing  the  thunder  by  five. 

Frequently  in  the  evening  flashes  called  heat  lightning 
are  seen  near  the  horizon.  These  are  due  to  the  reflection 
on  clouds  of  flashes  of  lightning  in  a  storm  which  is  below 
the  horizon.  Thunder-storms  occur  sometimes  in  winter. 
They  are  very  prevalent  in  the  tropics. 


ELECTRICAL   COMMUNICATION 


165 


81.   Electrical  Communication.  —  Experiment  87.  — Attach  one 

end  of  a  wire  to  a  pole  of  a  dry  cell  and  the  other  end  to  one  of  the 

binding  posts  of  a  telegraphic  sounder.     From  the  other  binding  post 

of  the  sounder  lead  a  wire  to  the  binding  post  of  a  telegraphic  key. 

Connect  the  free  binding  post  of  the  key  with 

y°«y|l  the  free  pole  of  the  battery  (Fig.  76).     When 

f    Bj  the  key  is  pushed  down,  the  circuit  is  closed  and 

— ^|  the  sounder  clicks.     If  a  relay  can  be  procured, 

J  remove  the  sounder  and  connect  two  of  the  bind- 


Fig.  76. 


Fig.  77. 


ing  posts  of  the  relay  in  the  same  way  that  the  sounder  was  connected. 
Connect  one  of  the  free  binding  posts  of  the  relay  with  a  binding 
post  of  the  sounder  and  the  other  binding  post  with  the  pole  of  a 
dry  cell.  Connect  the  other 
pole  of  the  dry  cell  with  the 
free  binding  post  of  the 
sounder.  When  the  key 
closes  the  circuit  through 
the  relay,  the  circuit  through 
the  sounder  and  its  dry  cell 
is  closed  by  the  relay  (Fig. 
77)  and  the  sounder  clicks. 


Fig.  78. 


This  is  the  usual  arrange- 
ment in  a  simple  telegraph 
office.  The  sounder  in  the  first  part  of  the  above  experiment  can  be 
replaced  by  an  electric  bell  (Fig.  78)  and  the  key  by  a  push  button, 
thus  showing  the  arrangement  of  the  ordinary  doorbell. 

Electricity  can  be  developed  by  chemical  action  as  well 
as  by  friction,  and  many  different  kinds  of  electrical  cells 
have  been  invented.  The  most  simple  of  these  is  a  sheet 


166 


FIRST   YEAR   SCIENCE 


Fig.  79. 


of  copper  and  a  sheet  of  zinc  placed  so  that  they  do  not 
touch  and  put  in  a  dish  containing  dilute  sulphuric  acid 
(Fig.  79).  The  current  developed 
by  this  cell  is  very  weak.  At  the 
present  time  dry  cells  are  used  for 
almost  all  ordinary  purposes  in  which 
electric  batteries  are  needed. 

The  history  of  the  development  of 
our  knowledge  of  primary  cells  and 
current  electricity  is  exceedingly  in- 
teresting and  important,  but  it  can- 
not be  dwelt  upon  here.  In  1832  an 
American,  Samuel  F.  B.  Morse,  invented  the  commercial 
telegraph.  This  was  the  first  step  in  the  wonderful  prog- 
ress that  has  been  made 
during  the  last  century 
in  communicating  rap- 
idly between  distant 
points.  The  necessary 
instruments  used  in  this 
form  of  communication 
are  a  sounder  (Fig.  80) 
and  a  key  (Fig.  81).  Fi£-  80- 

The  sounder  is  simply  an  electro-magnet  such  as  was  made 
in  Experiment  14,  arranged  to  attract  a  piece  of  soft  iron 

held  at  a  short  distance  from  it 
by  a  spring.  When  this  piece  of 
iron  is  attracted  toward  the  mag- 
net, it  strikes  on  another  piece  of 
iron,  making  a  click,  and  so  re. 
P.  g.  mains  drawn  to  the  magnet  as 

long  as  the  circuit  is  kept  closed. 

Thus  long  and  short  clicks  can  be  made.      Morse  arranged 
a  combination  of  these  long  and  short  clicks  to  represent 


TORNADOES  AND   WATERSPOUTS  167 

the  alphabet.  Thus  he  was  able  to  send  words  from  one 
station  to  another.  Experiment  87  illustrates  how  a  simple 
telegraph  can  be  arranged. 

Many  improvements  have  been  made  since  Morse  first 
sent  a  dispatch  between  Washington  and  Baltimore,  but 
his  dot-and-dash  alphabet  and  the  electro-magnet  sounder 
and  the  key  are  still  in  use.  Since  1832,  the  land  has 


WIRELESS  TELEGRAPH  STATION,  Los  ANGELES. 

been  strung  with  telegraph  wires  and  the  ocean  girdled 
with  cables,  and  now  an  important  event  occurring  in  any 
part  of  the  earth  is  known  almost  instantly  in  all  other 
parts.  The  telephone,  the  wireless  telegraph  and  the  wire- 
less telephone,  all  electrical  devices,  have  added  to  the  ease 
of  communication  so  that  the  whole  earth  is  brought  into 
such  close  relation  that  every  part  knows  what  all  the 
other  parts  are  doing.  No  other  form  of  energy  which 
man  has  discovered  is  of  such  diversified  usefulness  as 
electricity. 

82.  Tornadoes  and  Waterspouts.  —  Sometimes  causes  like 
those  which  produce  a  thunder-storm  are  so  strongly 
developed  that  the  indraft  is  exceedingly  violent  and  a 


168 


FIRST   YEAR   SCIENCE 


furious  whirling  motion  is  produced.  Such  storms  are 
called  tornadoes.  The  warm  moist  air  rises  rapidly  and 
spreads  out  into  a  funnel-shaped  cloud  Vith  the  vertex 
hanging  toward  the  earth.  In  the  center  of  the  whirl  the 

air  pressure  is  much 
diminished  and  the  ve- 
locity of  the  inrushing 
whirling  wind  is  tre- 
mendous, being  often 
sufficient  to  demolish  all 
obstacles  in  its  path. 

The  length  of  the  path 
swept  over  by  a  tornado 
is  rarely  over  thirty  or 
forty  miles  and  the  width 
generally  less  than  a 
quarter  of  a  mile.  The 
rate  of  progress  in  the 
Mississippi  valley  is  from 
20  to  50  miles  an  hour, 
usually  in  a  northeasterly 
direction.  These  storms 
are  often  wrongly  called 
cyclones.  When  storms 
of  this  kind  occur  at  sea, 

a  water  column  is  formed  in  the  funnel-shaped  part  of  the 
storm  and  they  then  receive  the  name  of  waterspouts. 

83.  Cyclones.  —  In  the  belt  of  westerly  winds  are  found, 
as  has  already  been  noted,  large  storm  areas  called  cyclones. 
As  the  barometric  pressure  in  the  center  of  these  areas  is 
lower  than  that  of  the  surrounding  region,  they  are  marked 
"Low"  on  the  weather  maps.  Into  these  low-pressure 
areas  the  air  from  all  directions  is  moving,  but  on  account 
of  the  deflection  due  to  the  rotation  of  the  earth,  the  wind 


A  TORNADO. 
Notice  the  funnel-shaped  cloud. 


CYCLONES 


169 


does  not  blow  directly  into  them,  but  produces  great  whirls 
in  which  the  air  moves  spirally  inward  and  upward. 

The  rate  at  which  the  wind  blows  varies  in  different 
parts  of  the  whirl,  but  is  never  very  great.  In  the  north- 
ern hemisphere  the  rotary  movement  is  in  the  direction 
opposite  to  that  in  which  the  hands  of  a  watch  move, 


THE  EFFECTS  OF  A  TORNADO. 

The  iron  windmill  was  blown  across  the  cellar  and  protected  the  people 
who  had  fled  there  for  safety. 


while  in  the  southern  hemisphere  it  is  with  the  hands  of  a 
watch.  As  these  are  areas  of  ascending  air,  they  are 
storm  areas.  The  extent  of  the  precipitation  varies  in 
different  parts  of  an  area  according  to  the  direction  from 
which  the  ascending  air  has  come.  Note  the  direction, 
of  the  wind  and  the  rainfall  area  as  shown  on  the  map 
(page  172). 

Air  which  comes  from  the  continental  interiors  is  dry, 
while  that  from  the  oceans  contains  much  moisture,  some 


170  FIRST  YEAE   SCIENCE 

f* 

of  which  it  deposits  when  made  to  ascend.  These  whirls 
move  in  a  general  eastward  direction  with  varying  veloc- 
ities, but  averaging  about  20  or  30  miles  per  hour.  To 
these  is  due  the  larger  part  of  the  rain  which  falls  in 
middle  latitudes.  Areas  of  high  pressure  in  which  the 
air  moves  spirally  downward  and  outward  from  the  center 


REMAINS  OF  FARM  BUILDINGS  DESTROYED  BY  A  TORNADO. 

as  has  already  been  stated  (§  74)  are  called  anti- cyclones. 
These  are  areas  of  dry,  cold  weather. 

84.  Paths  of  Cyclonic  Storms  across  the  United  States.  — 
The  map  on  page  172  shows  the  paths  of  a  large  number  of 
cyclonic  storms  across  the  United  States.  It  will  be  seen 
from  this  that  although  these  paths  vary  considerably,  yet 
the  general  direction  is  a  little  north  of  east.  The  move- 
ment of  the  cyclone  is  in  the  direction  of -the  prevailing 
winds  of  the  middle  latitudes. 

In  summer  time  the  average  rate  of  motion  of  the  cy- 
clone across  the  continent  is  about  500  miles  per  day, 
while  in  winter  it  is  800.  The  velocity  of  the  wind  in  the 


WEATHER   CHANGES 


171 


cyclone  is  also  much  less  in  summer  than  in  winter,  as  the 
difference  in  pressure  between  the  low  and  high  areas  is 
much  less.  The  changes  in  temperature  as  the  storms 
pass  are  greater  in  winter 
than  in  summer  since  the 
regions  from  which  the 
northerly  and  southerly 
winds  flow  in  toward  the 
center  of  low  pressure 
vary  more  in  their  tem- 
peratures. 

85.  Sudden  Weather 
Changes.  —  In  middle  lati- 
tudes there  often  occur, 
particularly  in  winter, 
sudden  changes  in  the 


WATERSPOUT  SEEN  OFF  THE  COAST 
OF  NEW  ENGLAND. 


temperature  of  20°  or 
more  in  a  few  hours.  In 
our  own  country,  if  the  temperature  falls  20°  or  more  in 
24  hours,  reaching  a  point  lower  than  32°  F.  in  the  north 
or  lower  than  40°  in  the  south  it  is  known  technically  as 
a  cold  ivave,  and  there  is  a  special  flag  (Fig.  82)  displayed 
by  the  Weather  Bureau  to  indicate  the  ap- 
proach of  such  a  change. 

When  these  waves  extend  over  the  southern 
part  of  the  country,  they  are  very  destructive 
to  the  orange  groves  and  delicate  crops  and  are 
known  as  "freezes."     A  notable  freeze  of  this 
kind   occurred    in    1886    and    did    tremendous 
damage  to  the  orange  groves  of  Florida.      So  great  was 
the  effect  upon  this  important  industry  throughout  the 
orange  belt  that  for  years  afterward  the  "freeze"  was  the 
date  from  which  events  were  reckoned. 

If   the  northwesterly  wind   which  brings  on  the  cold 


WEATHER   CHANGES 


173 


wave  is  accompanied  by  snow,  it  is  called  a  blizzard,  and  on 
the  plains  and  prairies,  where  the  wind  has  a  clear  sweep, 
it  is  much  dreaded.  Cattle  and  men,  when  caught  in  it, 
frequently  perish.  In  southern  Europe  the  coldest  winds 


are  from  the  Siberian  plains  and  are  therefore  northeasters. 
In  the  United  States  the  cold  area  is  at  the  southwest  and 
rear  of  the  cyclone,  whereas  in  Europe  it  is  at  the  north 
and  front. 

When,  instead  of  the  strong,  cold  northwest  winds 
which  blow  into  the  rear  of  a  cyclonic  area  and  in  the 
colder  seasons  may  produce  a  cold  wave,  there  is  a  pro- 
longed movement  of  highly  heated  air  from  the  south  into 
the  front  of  the  low  pressure,  as  sometimes  occurs  dur- 
ing the  warm  months,  the  "hot  spells  of  summer"  are 
caused.  The  air  is  sultry,  exceedingly  hot  and  oppressive. 
Sunstrokes  and  prostrations  from  heat  are  common. 
The  "  hot  winds "  of  Texas  and  Kansas,  the  Santa  Ana 
of  lower  California  and  the  siroccos  of  southern  Italy 
are  intensified  examples  of  these  winds.  All  sudden 


174  FIRST   YEAR   SCIENCE 

weather  changes  of  this  kind  are  due  to  atmospheric  con- 
ditions related  to  areas  of  low  pressure. 

86.  Weather  Forecasting.  —  The  data  necessary  for  fore- 
casting   the    weather   are    telegraphed   to   the    Weather 
Bureau  Stations  every  day,  and  a  record  of  them  placed 
on  the  weather  map.     The  observations  recorded  on  these 
maps  furnish  the. forecasters  with  all  the  information  ob- 
tainable as  to  what  the  weather  of  the  future  is  to  be.     It 
has  already  been  stated  that  the  dominant  cause  of  our 
weather  conditions  is  the  eastward  movement  of  cyclones 
and  anti-cyclones. 

If  the  direction  and  rate  of  motion  of  these  can  be  deter- 
mined the  weather  of  those  places  which  are  likeljr  to  come 
under  their  influence  can  be  foretold  with  a  good  deal  of 
accuracy.  If  a  cyclone  were  central  over  the  lower  Mis- 
sissippi valley  with  an  anti-cyclone  to  the  west  of  it,  we 
should  expect  that  the  southerly  and  southeasterly  winds 
and  rains  to  the  east  and  southeast  of  the  Mississippi  would 
gradually  change  to  fair  weather  and  westerly  winds  with 
increasing  cold,  as  the  cyclonic  area  was  replaced  by  the 
anti-cyclonic. 

The  rate  at  which  the  change  would  take  place  would 
depend  upon  the  rapidity  of  the  movements  of  the  two 
areas  of  high  and  low  pressure,  and  the  order  of  change  in 
the  direction  of  the  winds  would  depend,  for  any  place, 
upon  the  directions  taken  by  the  centers  of  these  areas. 
The  direction  of  movement  and  the  rapidity  of  movement 
of  the  cyclonic  areas  are,  therefore,  two  of  the  chief  factors 
which  enter  into  the  prediction  of  the  weather.  There  is 
usually  an  increase  in  the  intensity  of  the  storm  as  the 
Atlantic  coast  is  approached. 

87.  Climate.  —  The  average  succession  of  weather  changes 
throughout    the   year,  considered    for   a   long    period    of 
years,  constitutes  the  climate.     Thus,  if  the  average  tern- 


EFFECT  OF  CLIMATE 


175 


perature  of  a  place  throughout  the  year  has  for  a  long 
period  been  found  to  be  high,  and  the  rainfall  large  and 
uniformly  distributed,  the  place  is  said  to  have  a  hot  and 
humid  climate.  The  climate  is  a  generalized  statement 
of  the  weather.  Two  places  may  have  the  same  average 
temperature  throughout  the  year  without  having  the  same 
climate,  as  in  one  the  temperature  may  be  quite  uniform 
and  in  the  other  very  high  at  one  season  and  very  low 
at  another.  Many  factors  enter  into  the  making  up  of  a 
comprehensive  statement  of  climate. 

88.   Effect  of  Climate  upon  Animals  and  Plants.  —  Plants 
are  greatly  affected  by  climate.     The   ornamental  palm 


A  SOUTHERN  COTTON  FIELD. 


and  orange  trees,  which  are  sometimes  cultivated  in  the 
north,  have  to  be  protected  from  the  winter  cold  with 
great  care,  whereas  in  southern  climates  they  grow  and 
flourish  as  the  apples  and  pears  do  in  the  north.  Corn 
and  wheat  are  the  staple  agricultural  products  of  the 


176 


FIRST   YEAE   SCIENCE 


northern  part  of  the  United  States,  while  cotton,  rice  and 
oranges  are  of  the  southern  part. 

If  plants  are  to  flourish,  the  heat  and  cold  and  amount  of 
moisture  must  be  such  that  the  seeds  can  ripen  and  find  suit- 
able conditions  for  preservation  and  growth  in  succeeding 
years.  Plants  like  the  cactus  and  the  Yucca  Palm  which 


YUCCA  PALM. 

thrive  in  the  dry  and  desert  regions  of  New  Mexico  and 
Arizona  would  soon  die  in  the  moist  climate  of  Louisiana. 
As  animals  live  upon  plants  or  .upon  other  animals,  the 
plants  must  supply  the  food  of  the  plant-eating  animals 
and  through  these  of  the  animal  eaters.  Thus,  the  dis- 
tribution of  plants  has  a  great  effect  upon  the  animal  life. 
Animals  that  eat  grass  will  not  live  in  a  desert,  neither 
will  animals  that  eat  nuts  live  in  a  prairie,  where  there 
are  no  nut-bearing  plants. 


EFFECT  OF  CLIMATE 


177 


CAMEL. 


Temperature  and  moisture  also  affect  animals  as  well 
as  plants,  although  animals  can  hide  away  from  the  scorch- 
ing sun  and  move  about  for  water  as  plants  cannot.  An 

animal    like    the    polar     __^ 

bear,  whose  coat  has  be- 
come   thick   to   protect 
him    from    great    cold, 
would  soon  pine  away 
and  die,  if  transferred  to 
the   jungles   of   Africa, 
where  his  fellow  flesh- 
eater,  the  lion,  revels  in 
joyful    existence.       To 
the  camel  of  the  desert 
the  damp,  grassy  savan- 
nas would  be,  indeed,  a  dreary  waste  and  verdant  cemetery. 
Thus,  when  once  plants  and  animals  have  become  adapted 
to  certain  climatic  conditions,  they  cannot  flourish  if  placed 
under  very  different  conditions. 

89.  Effect  of  Climate  upon  Man.  —  Since  man  can  change 
his  outer  covering  of  clothes  whenever  he  desires  and  is  able 
to  carry  with  him  and  store  for  long  periods  his  necessary 
food,  and  by  artificial  means  raise  or  even  lower  the  tem- 
perature of  the  space  in  which  he  lives,  he  is  not  nearly  so 
dependent  upon  climate  as  are  either  plants  or  animals. 

The  same  man  can,  for  a  time,  live  in  arctic  regions  or 
in  the  tropics.  Men  can,  moreover,  by  centuries  of  effort 
become  accustomed  to  the  climate  of  almost  any  part  of 
the  globe.  The  Laplander  and  the  South  Sea  Islander 
both  flourish  in  their  adopted  homes.  Neither  of  these, 
however,  has  attained  to  the  highest  development  of 
which  man  is  capable.  The  rigorous  severity  of  the  cli- 
mate saps  the  energies  of  one  and  its  uniform  geniality 
lulls  the  ambition  of  the  other. 


178 


FIRST   TEAR    SCIENCE 


In  temperate  latitudes,  where  there  is  need  of  providing 
for  the  winter  when  plants  do  not  grow  and  when  food 
is  hard  to  find,  where  the  blood  is  stirred1  by  the  invigo- 
rating cold,  and  where 
nature  in  her  ever  chang- 
ing mood  gives  zest  to 
living,  is  the  place  where 
man  has  attained  his 
highest  achievements. 
Here  the  fight  for  exist- 
ence does  not  require 
all  man's  energy,  and  the 
.  bounty  of  nature  does  not 
free  him  from  strenuous 
effort.  Thus  it  is  seen 
that  even  upon  man  the 
influence  of  climate  is 
great.  How  great,  it  is 
impossible  fully  to  realize, 
so  complex  are  his  rela- 
tions. 

Summary.  —  The  atmosphere  is  just  as  important  to  life 
upon  the  earth  as  are  energy,  light,  heat,  water  and  land. 
Air  contains  oxygen  from  which  we  get  heat  and  energy, 
carbon  dioxide,  from  which  plants  build  up  their  tissues, 
and  nitrogen  which  dilutes  these  two. 

The  weight  of  air  is  not  usually  realized  because  it 
presses  uniformly  in  all  directions.  Air  expands  when 
heated ;  so  a  cubic  foot  of  warm  air  weighs  less  than  a 
cubic  foot  of  cold  air.  Warm  air  will  also  hold  more 
moisture  than  cold  air. 

The  pressure  of  air,  due  to  its  weight,  may  be  measured 
by  a  barometer.  The  heights  of  mountains  may  also  be 
measured  by  this  instrument,  as  there  is  less  air  above  a 


A  LAPLANDER. 


SUMMARY 


179 


high  mountain  than  above  a  low  one.  The  winds  are 
caused  by  changes  in  atmospheric  pressure;  their  prevail- 
ing direction  is  affected  by  the  earth's  rotation.  Certain 
winds  common  to  all  planets  are  called  planetary  winds; 
when  modified  by  cer- 
tain peculiarities  of  the 
earth  they  are  called 
terrestrial  winds.  Be- 
cause of  their  constancy 
and  their  aid  to  traffic, 
some  of  these  winds  are 
called  trade  winds. 
South  of  Asia  there  are 
winds  called  monsoons. 

When  very  moist  air 
cools,  it  cannot  hold  as 
much  moisture  as  when 
it  is  warm,  so  this  falls 
as  rain,  hail,  sleet  or 
snow.  The  rainfall 
varies  from  nothing  at 
all  in  some  places  to 
over  fifty  feet  a  year  in 
others.  In  the  United  States  the  north  Pacific  slope  has 
a  rainfall  of  about  seventy  inches  a  year  ;  the  south  Pacific 
slope  about  fifteen  inches  ;  the  eastern  slope  of  the  Rockies 
is  very  dry  ;  and  the  Mississippi  valley  and  the  country  to 
the  east  of  it  have  a  rainfall  of  from  thirty  to  sixty  inches. 

Rainstorms  when  accompanied  by  thunder  and  light- 
ning are  called  thunder-storms.  Thunder  and  lightning  are 
caused  by  certain  clouds  having  a  higher  charge  of  elec- 
tricity than  others.  The  higher  charge  bursts  across  to 
the  lower  charge,  making  a  flash  of  lightning  and  a  roll 
of  thunder. 


A  SOUTH  SEA  ISLANDER. 


180  FIRST   YEAR    SCIENCE 

'  .  rf* 

When  the  wind  blows  spirally  and  with  great  violence, 

•sweeping   everything   before   it,    it   is   called  a   tornado. 

This  is  popularly  known   as  a  cyclone,  but  a  cyclone  is 

really  a  very  large  circular  storm  area.     Real  cyclones  do 

no  damage. 

All  these  storms  have  a  marked  effect  upon  the  weather, 
the  changes  of  which  are  forecast  by  the  weather  bureau. 
The  general  weather  conditions  of  a  place  determine  its 
climate.  The  climate  of  any  place  has  a  great  effect  upon 
plants,  animals  and  man. 

• 
QUESTIONS 

What  are  the  characteristics  and  principal  uses  of  the  three  most 
abundant  gases  in  the  atmosphere  ? 

How  can  it  be  shown  that  air  has  weight  and  exerts  pressure  ? 

What  effect  has  heat  upon  the  weight  and  volume  of  air? 

WThat  effect  has  pressure  upon  the  weight  and  volume  of  air  ? 

How  do  the  two  kinds  of  barometer  ordinarily  used  differ  in  con- 
struction ? 

Where  have  you  ever  observed  the  effects  of  adiabatic  heating? 

What  experiences  have  you  ever  had  which  show  that  hot  air  will 
hold  more  moisture  than  cold  air  ? 

How  are  the  light  and  heat  rays  from  the  sun  affected  by  the 
atmosphere  ? 

Name  and  explain  the  chief  causes  that  affect  the  temperature  of  a 
place. 

What  is  the  cause  of  wind  and  how  is  its  velocity  measured  ? 

How  are  the  winds  influenced  by  the  earth's  rotation? 

In  going  from  Boston  to  Cape  Horn  through  what  wind  belts 
would  a  sailing  vessel  pass  and  how  would  her  progress  be  affected  by 
the  winds  in  these  belts  ?  What  weather  conditions  would  she 
probably  encounter? 

At  what  season  of  the  year  would  a  steam  vessel  equipped  with 
sails  make  the  best  time  to  India  by  way  of  the  Suez  canal?  Why  ? 

Upon  what  does  the  rainfall  of  a  place  largely  depend  ? 

How  is  the  rainfall  of  the  United  States  distributed  ? 

What  is  the  relation  between  lightning  and  electricity  ?  What  is 
thunder  ? 


QUESTIONS  181 

With  what  electrical  devices  are  you  familiar  ? 

What  are  the  principal  differences  between  a  tornado  and  a 
cyclone  ? 

What  are  the  chief  effects  of  climate  upon  plants  and  animals? 

State  the  climatic  conditions  which  are  best  for  man's  develop- 
ment. 


CHAPTER   VI 


THE  LIVE  PAKT  OP   THE  EARTH 

90.   Plants  and  Animals.  —  Plants  and  animals  are  com- 
binations of  the  earth's  elements  endowed  with  life.     By 

means  of  the  sun's  en- 
ergy they  are  able,  the 
plants  directly  and  the 
animals  indirectly,  to 
do  both  internal  and 
external  work  which  re- 
sults in  growth,  repro- 
duction and  other  ac- 
tivities. Since  plants 
and  animals  are  entirely 
dependent  upon  the 
earth  and  sun  for  their 
existence,  they,  like 
other  earth  and  sun 
phenomena,  should  be 
studied  in  this  course. 

91.  Plants.  — Although 
in  their  lower  micro- 
scopical forms  it  is  very 
difficult  to  distinguish 
between  plants  and  ani- 


THB  ROCKY  MOUNTAIN  GIANT. 

The  monarch  of  all  plants,  93  feet 
around  at  the  base.     Notice  the  cav- 
alry at  the  foot. 


mals,  yet  the  forms 
ordinarily  seen  differ 
greatly.  Most  plants  are  fixed  and  consist  of  root,  stem 
and  leaves,  while  most  animals  are  movable  and  possess  a 

182 


PLANT  ROOTS 


183 


variety  of  different  parts.  But  some  plants,  like  the  sea- 
weeds, appear  to  have  no  roots  ;  some,  like  the  dandelion, 
no  plant  stem,  and  some,  like  the 
cactus,  no  leaves. 

If  we  dig  around  the  base  of  a  tree, 
we  find  in  the  soil  a  network  of  roots 
holding  firmly  erect  a  pillar-like  stem 
with  branches  bearing  a  profusion  of 
leaves.  If  we  examine  these  divisions 
carefully,  we  shall  find  that  each  has 
a  distinct  part  to  play  in  the  life  work 
of  the  tree.  We  shall  also  find  (1)  that 
plants  as  well  as  animals  need  air,  water 
and  other  kinds  of  food,  (2)  that  plants, 
like  animals,  take  in,  digest  and  as- 
similate food,  and  (3)  that  each  in  the 
higher  forms  has  parts  which  are  par- 
ticularly adapted  for  doing  these  differ- 
ent kinds  of  work. 

92.  Plant  Roots.  —  Plant  roots  not 
only  usually  secure  the  plant  to  the 
ground  so  that  the  stem  may  be  sup- 
ported, but  they  take  up  food  from  the 
soil  and  pass  it  on  to  the  rest  of  the 
plant.  In  most  plants  all  the  foods 
except  carbon  and  oxygen  are  taken  in 
by  the  roots.  The  soil  elements  that 
the  plants  must  have  are  nitrogen, 
potassium,  calcium,  magnesium,  phosphorus,  sulphur 
and  iron.  Water  is  composed  of  hydrogen  and  oxygen, 
while  carbon,  the  other  necessary  element,  is  taken 
from  the  air.  The  soil  elements  must  be  in  soluble 
chemical  combinations,  such  as  nitrates,  phosphates,  sul- 
phates and  so  on. 


A  TYPICAL  PLANT. 

Showing  root,  stem, 
leaf  and  flower. 


184  FIRST  YEAR  SCIENCE 

Experiment  88.  —  Fill  three  2-quart  fruit  jars  each  about  half  full  of 
distilled  water.  Add  to  the  water  in  the  first  of  these  ^  gram  of 
potassium  nitrate,  \  gram  iron  phosphate,  Tlg%  grarn  calcium  sulphate 
and  TV2o  gram  magnesium  sulphate.  Add  to  the  water  in  the  second 
jar  the  same  ingredients  with  the  exception  of  the  potassium  nitrate. 
Replace  this  by  potassium  chloride.  Put  the  three  jars  where  they 
will  receive  plenty  of  sunlight  and  warmth  and  place  in  each  a  slip 
of  Wandering  Jew  about  10  inches  long.  Note  which  slip  grows 
the  most  thriftily.  In  the  third  jar  there  is  no  mineral  food,  in  the 
first  all  of  this  food  which  is  necessary  and  in  the  second  all  the 
necessary  food  except  nitrogen. 

In  Experiment  88,  it  was  found  that  in  the  distilled  water 
the  plant  made  but  little  growth.  It  did  not  thrive  when 
the  nitrogen  was  lacking,  but  grew  very  well  when  all  the 
necessary  elements  were  present.  All  plant  foods  must 
be  in  dilute  solution  before  plants  can  appropriate  them. 

Experiment  89.  —  In  another  fruit  jar  make  a  strong  solution  of 
potassium  nitrate  or,  as  it  is  commonly  called,  saltpeter.  Place  in  this 
a  slip  of  Wandering  Jew  as  was  done  in  the  previous  experiment. 
Does  the  slip  grow  well  ?  It  has  a  great  abundance  of  nitrogen,  which 
was  found  so  important.  Place  in  a  similar  strong  solution  a  grow- 
ing beet  or  radish  freshly  removed  from  the  ground.  Notice  how  it 
shrivels  up.  Place  a  similar  beet  or  radish  in  water.  It  is  not  similarly 
affected.  What  is  the  effect  of  strong  solutions  on  plants? 

If  the  solution  is  too  strong,  as  seen  in  Experiment  89, 
the  plant  cannot  use  it.  This  is  the  reason  many  alkali 
soils  will  not  support  plants.  The  alkali  salts  are  so 
readily  soluble  that  the  soil  water  becomes  a  solution 
stronger  than  the  plants  can  use. 

Experiment  90.  —  Place  three  or  four  thicknesses  of  colored  blotting 
paper  en  the  bottom  of  a  beaker.  Thoroughly  wet  the  paper  and 
scatter  upon  it  several  radish  or  other  seeds.  Cover  the  beaker  with 
a  piece  of  window  glass  and  put  in  a  warm  place.  Allow  it  to  stand 
for  several  days,  being  sure  to  keep  the  blotting  paper  moist  all 
the  time.  When  the  seeds  have  sprouted,  examine  the  rootlets,  with 
a  magnifying  glass  or  low  power  microscope,  for  the  root  hairs  which 


PLANT  ROOTS  185 

look  like  fuzzy  white  threads.  Touch  the  root  hairs  with  the  point 
of  a  pencil.  They  cannot,  like  the  rest  of  the  root,  stand  being  dis- 
turbed. On  what  part  of  the  root  do  the  root  hairs  grow  ?  As  the 
blotting  paper  dries,  what  happens  to  the  root  hairs? 

Plant  roots  are  prepared  particularly  by  the  little  root 
hairs,  which  were  examined  in  Experiment  90,  to  take  the 
film  of  water  which  surrounds  the  soil  particles  and  carry 
this  water  to  the  stem  and,  through  it,  to  the  leaves.  The 
water  which  the  roots  take  from  the  soil  is  a  dilute  solu- 
tion containing  the  plant  food  substances.  Not  only  do 
roots  absorb  the  water  from  the,  soil,  but  they  secrete 
weak  acids  which  aid  in  dissolving  the  mineral  substances 
which  the  plants .  need.  This  can  be  seen  where  plant 
roots  have  grown  in  contact  with  polished  surfaces,  such 
as  marble.  These  surfaces  are  found  to  be  etched. 

Experiment  91.  —  Cut  a  potato  in  two.  Dig  out  one  of  the  halves 
into  the  shape  of  a  cup  and  scrape  off  the  outside  skin.  Fill  the  potato 
cup  about  |  full-  of  a  strong  solution  of  sugar.  Mark  the 
height  of  the  sugar  solution  by  sticking  a  pin  into  the  inside 
of  the  cup.  Place  the  cup  in  a  dish  of  water.  The  water 
should  stand  a  bit  lower  than  the  sugar  solution  in  the  potato 
cup.  After  the  cup  has  stood  in  the  water  for  some  time, 
notice  the  change  in  the  height  of  the  denser  sugar  solution. 

Experiment  92.  —  Bore  a  f -inch  hole  3  or  4  inches  deep  in 
the  top  of  a  carrot.  Scrape  off  the  outside  skin  and  bind 
several  strips  of  cloth  around  to  keep  the  carrot  from  split- 
ting open.  Fit  the  hole  with  a  one-hole  rubber  stopper 
having  a  glass  tube  about  1  meter  long  extending  through 
it.  Fill  the  hole  in  the  carrot  with  a  strong  sugar  solution 
colored  with  a  little  eosin  and  strongly  press  and  tie  in  the 
stopper.  The  sugar  solution  will  be  forced  a  short  distance 
up  the  tube  by  the  insertion  of  the  stopper.  Mark  with  a  rubber  baud 
the  height  at  which  it  stands.  Submerge  the  carrot  in  water  and  allow 
it  to  stand  for  a  few  hours.  Mark  occasionally  the  height  of  the  column 
in  the  tube.  Taste  the  water  in  which  the  carrot  was  submerged. 
There  has  been  an  interchange  of  liquids  within  and  without  the 
carrot. 


186 


FIRST   YEAR   SCIENCE 


The  plant  root  takes  up  its  water  in  the  same  way  the 
water  was  taken  into  the  sugar  solution  of  the  potato  cup 
or  of  the  carrot.  The  water  or  sap  within  the  substance 
of  the  root  is  denser  than  the  soil  water,  just  as  the  sugar 
solution  was  denser  than  the  water  outside.  It  has  been 
found  that  whenever  two  liquids  or  gases  are  separated 
by  an  animal  or  plant  membrane,  there  is  an  interchange 
of  the  liquids  or  gases,  the  less  dense  liquid  or  gas  passing 
through  more  rapidly.  This  is  called  osmosis  and  is  of 
the  greatest  importance  to  both  plants  and  animals. 

All  animals  and  plants  are  made  up  of  exceedingly 
minute  parts,  called  cells.  Fig.  84  shows  the  cells  in  a  leaf 

and  the  leaf  hairs  greatly 
magnified.  The  higher 
plants  and  animals  are 
composed  of  vast  num- 
bers of  these  cells.  The 
cell  usually  has  a  thin 
cell  wall,  which  in  living 
and  growing  cells  in- 
closes a  colorless  semi- 
fluid substance  called 
protoplasm.  This  pro- 
Pig  84.  toplasm  is  the  living  part 
of  the  plant.  It  is  found 

in  all  the  cells  where  growth  is  taking  place,  where  plant 
substances  are  being  made,  or  where  energy  is  being  trans- 
formed. It  has  the  power  of  dividing  and  forming  new 
cells,  and  it  is  in  this  way  that  the  plants  grow. 

The  little  root  hairs  are  one  kind  of  plant  cells.  They 
consist  of  a  thin  cell  wall  within  which  is  protoplasm  and 
cell  sap,  a  solution  of  different  plant  foods.  Since  the  pro- 
toplasm and  cell  sap  are  denser  than  the  soil  water,  more 
liquid  moves  into  the  cell  than  from  it.  A  little  of  the 


PLANT  ROOTS 


187 


cell  solution  does  move  out,  however,  and  it  is  this  which 
helps  to  dissolve  the  soil  particles.  The  protoplasm  in  the 
cell  regulates  to  some  extent  the  interchange  of  liquids. 

Experiment  93.  —  Cut  off  the  stem  of  a  thrifty  geranium,  begonia, 
or  other  plant  an  inch  or  two  above  the  soil.     Join  the  plant  stem  by 
a  rubber  tube  to  a  glass  tube  a  meter  long,  of  about  the  same  diame- 
ter as  the  stem.     See  that  the  rubber  tube  clings  strongly 
to  both  glass  tube  and  stem.      It  may  be  best  to  tie  it 
tightly  to  these.     Support  the  glass  tube  in  a  vertical  posi- 
tion above  the  stem  and  pour  into  it  sufficient  water  to  rise 
above  the  rubber  tube.      Note  the  position  of  the  water 
column.      Thoroughly    water    the   soil   about  the  plant. 
Watch  the  height  of  the  water  column,  marking  it  every 
few  hours. 

The  water  taken  in  by  the  roots  passes  on  from 
cell  to  cell  by  osmotic  action  and  rises  in  the  stem    p^     8^ 
in  the  same  way  that  the  water  rose  in  the  tube 
attached  to  the  stem  of  the  growing  plant  in  Experiment 
93.     The  root  pressure,  together  with  capillarity,  as  seen 

in  Experiment  54,  will 
account  for  the  rise  of 
the  sap  in  lowly  plants, 
but  the  cause  of  the  rise 
of  the  sap  to  the  top  of 
lofty  trees  is  difficult  to 
understand. 

Roots  extend  them- 
selves through  the  soil 
by  growing  at  the  tips. 
Here  the  cells  are  rapidly 
dividing,  forming  new  cells  and  building  root  tissue.  As 
water  is  so  essential,  they  are  always  seeking  it  and  ex- 
tending themselves  in  the  direction  where  it  is  to  be  found. 
This  causes  them  to  extend  broadly  and  to  sink  deeply 
(Fig.  86).  A  single  oat  plant  has  been  found  to  have  an 


86- 


188  FIRST   TEAR   SCIENCE 

** 

entire  root  extension  of  over  150  feet.  This  seeking  of 
the  roots  for  water  sometimes  causes  the  roots  of  trees  to 
grow  into  drain  pipes  and  stop  them  up.  *•  For  this  reason 
the  planting  of  certain  trees  near  sewer  pipes  is  often 
prohibited. 

Experiment  94.  — Boil  some  water  so  as  to  drive  out  the  air  and  after 
it  has  become  cool  fill  a  2-quart  fruit  jar  half  full.  Dissolve  in  this 
all  the  necessary  plant  food  as  was  done  in  Experiment  88,  making 
the  solution  the  same  strength.  Place  in  this  a  slip  of  Wandering 
Jew.  Pour  over  the  surface  of  the  water  a  layer  of  castor  oil  or  sweet 
oil.  Place  this  jar  alongside  the  slip  in  the  other  complete  food  solu- 
tion, Experiment  88.  Both  slips  have  the  same  conditions  except 
that  the  oil  keeps  out  the  air  from  the  roots  of  one  of  them.  Does 
the  absence  of  air  affect  the  growth  of  the  slip  V 

As  the  tips  of  the  roots  are  delicate,  it  can  be  readily  seen 
that  if  they  are  to  grow  readily  the  soil  around  them  must 
be  mellow.  It  was  also  seen  in  Experiment  94,  that  if 
roots  are  to  grow  they  must  have  air,  another  reason  for 
keeping  the  soil  mellow. 

Roots  are,  however,  not  simply  absorbers  of  water  and 
dissolved  food.  Some  of  them  act  as  storehouses  for  the 
food  that  the  plant  has  prepared  for  future  use.  Beets, 
carrots,  parsnips,  turnips  and  sweet  potatoes  are  examples 
of  roots  which  store  food  ready  for  the  rapid  growth  of 
the  next  year's  plant. 

93.  Steins. — Experiment  96.  —  Examine  a  corn  stalk.  Notice 
how  and  where  the  leaves  are  attached  to  the  stem.  Do  the  alternate 
leaves  come  from  the  same  side  of  the  stem  ?  Cut  a  cross  section  of 
the  stalk.  Notice  the  outside  hard  rind,  the  soft  pithy  material  and 
the  small  firmer  points  scattered  about  in  the  pith.  Cut  a  section 
lengthwise  of  the  stalk  and  notice  how  these  small  firmer  points  are 
related  to  the  lengthwise  structure  of  the  stem. 

Cut  off  a  young  growing  corn  stalk  and  place  the  cut  end  in  water 
colored  by  eosin  or  red  ink.  Allow  it  to  stand  for  some  time  and 
then  cut  the  stalk  off  an  inch  or  two  above  the  surface  of  the  water. 
How  have  "the  firmer  points  "  been  affected?  If  possible,  make  the 


PLANT  STEMS 


189 


same  observations  and  experiments  on  the  stem  of  a  small  seedling 
palm  tree. 

Experiment  96.  —  Examine  a  piece  of  the  growing  young  stem  of  a 
willow,  apple  tree  or  other  woody  stem  that  shows  several  leaf  scars. 
Is  the  arrangement  of  the 
leaves  the  same  as  in  the  corn 
stalk  ?  Cut  a  cross  section  of 
this  stem  and  examine  it. 
Does  it  resemble  the  cross 
section  of  the  corn  stalk? 
Strip  off  a  piece  of  the  bark 
and  compare  it  with  the  rind 
of  the  corn  stalk.  Examine 
carefully  the  smooth,  slippery 
surface  of  the  wood  just  be- 
neath the  bark.  This  is  the 
cambium  layer. 

Examine  the  firm  wood 
beneath  this  layer.  Where 
is  the  pith  in  this  stem  ? 
With  a  lens  you  may  be  able 
to  see  lines  radiating  from 
the  pith  to  the  circumference 
of  the  stern.  These  are  called 
the  pith  rays.  Cut  a  length- 
wise section  of  the  stem  and 
examine  it.  Are  there  any 
fiber-like  bundles  as  in  the 
corn  stalk?  Cut  off  a  piece  of  the  stem  already  examined  having  the 
bark  on  it,  or  a  piece  of  sunflower  stem,  and  place  the  end  of  it  in 
colored  water.  Allow  it  to  remain  for  some  time  arid  then  cut  a  cross 
section  above  the  point  where  it  was  in  the  water.  Has  the  water  risen 
and  colored  this  cross  section  as  it  did  the  cross  section  of  the  corn  stalk  ? 

Stems  vary  greatly  in  the  positions  they  assume.  Some 
rise  firmly  erect  from  the  root,  like  the  oak  and  the  pine ; 
some  cling  to  supports,  like  the  grape  and  the  ivy ;  some 
twine  around  supports,  like  the  bean ;  some  creep  upon 
the  ground,  like  the  strawberry ;  some  grow  in  the  form 


A  PINE  TREE. 
Notice  the  erect  position  of  the  stem. 


190 


FIRST   YEAR   SCIENCE 


of  a  thickened  bulb  like  the  onion  (Fig.  87)  ;  some,  like 
the  cacti,  assume  a  fleshy  leaflike,  though  leafless  form  ; 
some,  like  the  nut  grass,  Johnson  grass  and 
witch  grass,  grow  underground  and  send 
up  shoots,  and  some  sterns  store  up  food 
underground  in  tubers,  like  the  potato 
(Fig.  87),  from  which  the  next  year's 
plant  may  grow. 

Notwithstanding  all  the  diversity  shown 
by  the  stem,  its  principal  functions  are  to 
support  the  leaves,  so  that  they  will  best 
be  exposed  to  the  light,  and  to  conduct 
the  food  solutions  from  the  root  to  the 
leaves.  The  part  of  the  stem  through 
which  the  cell  sap  flows  was  seen  in 
Experiments  95  and  96. 

There  are  two  great  types  of  stems,  one 
represented  by  the  corn  stalk  and  palm 
and  the  other  by  the  willow,  sunflower  and 
bean.  On  account  of  the  structure  of  the 
seeds  these  are  called,  respectively,  mono- 
cotyledonous  (one  seed  leaf)  and  dicotyledonous  (two  seed 
leaves).  That  these  differ  greatly  in  their  appearance 
was  seen  in  Experiments  95 
and  96,  where  the  two  kinds 
of  stems  were  compared.  It 
was  also  found  in  these  ex- 
periments that,  in  the  first, 
the  red  colored  water  that 


AN  IVY  BRANCH. 

Notice  the  tiny 
root-like  ap- 
pendages by 
which  it  clings 
to  its  support. 


Fig.  87. 


Fig.  88. 


took  the  place  of  the  sap  rose  in  the  fibrous  bundles  scat- 
tered through  the  pith,  while  in  the  second  it  rose  through 
the  woody  tissue  within  the  bark. 

Experiment  97. —  Examine   a  cross   section  of   a   hardwood  tree 
several  years   old,  and  if   possible  of  a  palm.     Notice  the  ring-like 


PLANT  STEMS  191 

arrangement  of  the  layers  in  one  and  the  absence  of  all  such  arrange- 
ment in  the  other. 

In  Experiment  97,  when  the  cross  section  of  a  dicoty- 
ledonous tree  was  examined,  it  was  found  to  be  composed 
of  circular  rings,  but  no  such  rings  are  found  in  the  cross 
section  of  the  monocotyledonous  tree.  When  later  we 


A  BANYAN  TREE. 

Some  of  its  branches  descend,  and  take  root  in  the  ground,  and  so  appear 

like  stems. 

examine  the  seeds  of  corn  and  bean,  we  shall  find  that 
they  also  differ  very  much. 

When  the  bark  is  removed  from  a  stem,  like  the  willow 
or  apple,  the  soft  smooth  layer  underneath  is  found  to  be 
composed  of  living  cells.  This  is  called  the  cambium 
layer.  During  the  season  of  growth,  these  cells  are  con- 
tinually subdividing  and  forming  new  cells,  thus  adding 
to  the  thickness  of  the  stem.  The  age  of  a  tree  can  be 


192 


FIRST   TEAR   SCIENCE 


determined  by  counting  these  rings.     No  such  layer  is 
found  in  the   monocotyledonous  stems.      Grafting   (Fig. 

89)  and-  budding  (Figs. 
90  and  91)  are  processes 
of  bringing  the  cambium 
layers  of  two  trees  of 
similar  kinds  in  contact 
and  keeping  them  pro- 
tected so  that  they  will 
grow  together.  In  this 
way,  many  of  our  finest 
species  of-  fruit  are  propagated. 

Experiment  98. — Examine  several  growing  stems  or  twigs  which 
have  buds  upon  them  and  notice  how  the  buds  are  arranged.  Is  the 
arrangement  the  same  in  all?  If  these  buds  grew  into  twigs  or 
leaves,  would  they  shade  each  other  ?  Is  there  a  bud  at  the  end  of 
the  twig  or  stem  ? 


Fig.  89. 


Fig.  90. 


Fig.  91. 


If  we  examine  the  tip  of  a  growing  stem  or  twig,  we 
shall  find  a  bud.  In  most  of  the  trees  and  shrubs  of 
temperate  regions  a  terminal  bud  is  formed  at  the  close  of 


PLANT  LEAVES 


193 


the  growing  season,  and  from  this  the  shoot  continues  to 
grow  the  following  season.  Buds  are  also  found  along 
the  length  of  the  stem  and  branches,  as  was  seen  in  Ex- 
periment 98.  These  are  lateral  buds  and,  since  they  are 
usually  found  in  the  axis  of  the  leaf,  at  the  angle  formed 
b}^  the  leaf  and  stem,  they  are  called  axillary.  In  some 
trees  the  terminal  buds  die  at  the  end  of  the  growing 
season,  and  the  next  year's  growth  is  due  to  one  of  the 
axillary  buds. 

94.  Leaves.  —  If  we  examine  the  arrangement  of  the 
leaves  on  a  plant  or  tree,  we  shall  see  that  they  do  not  lie 
one  directly  above  the 
other,  but  that  they  are 
so  arranged  as  not  to 
shade  each  other. 
Their  position  generally 
is  such  that  the  broad 
upper  surface  of  the  leaf 
receives  the  strong  light 
rays  perpendicularly  up- 
on it.  To  accomplish 
this,  the  leaves  in  many 
trees  are  arranged  spir- 
ally around  the  stem. 

The  stem  of  the  leaf 
itself,  in  some  parts  of 
the  tree,  often  grows 
long  and  twists  about, 
in  order  to  push  the  leaf  out  to  the  light  and  yet  not  let  it 
be  wrenched  away  by  the  wind.  The  horse-chestnut  is 
such  a  leaf.  In  some  plants,  like  the  sunflower,  the  younger 
leaves  follow  the  sun  all  day.  In  other  plants  the  rays  of 
the  sun  seem  to  be  too  bright  in  the  middle  of  the  day  and 
the  leaves  are  then  held  edgewise  to  the  light. 


DIFFERENT  FORMS  WHICH  LEAVES 
ASSUME 


194 


FIRST   YEAR   SCIENCE 


Fig.  92. 


A  striking  example  of  this  is  the  compass  plant,  the 

leaves  of  which  arrange  themselves  so  that  the  sun's  rays 
strike  the  broad  surface  iof  the  leaves  at 
night  and  morning  when  the  rays  are  not 
very  strong,  but  at  noon  the  edge  of  the 
leaf  is  toward  the  sun,  the  leaf 'thus  main- 
taining a  nearly  vertical  position  all  day, 
with  its  greatest  length  extending  in  a 
nearly  north  and  south  line.  It  is  the 
effort  to  regulate  the  amount  of  light  fal- 
ling on  the  leaf,  and  not  any  magnetic 
influence,  which  causes  the  leaf  to  point  in 

the  direction  of  the  compass  needle. 

The  shapes  of  the  leaves  vary  greatly  in  different  plants. 

Sometimes    they    assume    -very 

singular  forms,  as  in  the  pitcher 

plant    (Fig.    92)    and    Jack-in- 

the-pulpit.        Sometimes     they 

even    become    carnivorous,    as 

in  the  sundew  and  Venus  fly- 
trap. 

Around   the   margin    of    the 

sundew  leaf  and  on  the  inner 

surface  are  a  number  of  short 

bristles  each  having  at  the  end 

a  knob  which  secretes  a  sticky 

liquid.     As   soon   as  an   insect 

touches  one  of  these  knobs,  it 

sticks    to    the    knob    and    the 

other  bristles  begin  to  close  in 

upon  the  insect  and  hold  it  fast. 

Soon  the  insect  dies  and  the  leaf 

secretes   a   juice    which   digests   its   soluble   parts. 

In  the  Venus  flytrap  (Fig.  93)  the  leaf  terminates  in 


Fig.  93. 


PLANT  LEAVES 


195 


Fig.  94. 


a  portion  which  is  hinged  at  the  middle  and  has  on  the 
inside  of  each  half  three  short  hairs,  while  the  outside 
is  fringed  by  stiff  bristles.  As  soon  as  an  insect  touches 
the  hairs,  the  trap  closes  rapidly  upon  it  and 
stays  closed  until  it  is  digested,  when  the  trap 
again  opens.  Carnivorous  plants  of  this  kind 
usually  grow  in  places  where  it  is  difficult  to 
get  nitrogenous  foods,  and  they  have  adopted 
this  way  to  supply  the  need. 

Some  leaves   extend   themselves   into   spiny 
points,  like  the  thistle   (Fig.  94),  in  order  to 
keep  animals  from  destroying  the  plant,  or  they 
may  develop   a   sharp  cutting  edge,  like   some   grasses, 
or  emit  a  bad  odor,   or  have  a  repugnant  bitter  taste. 

The  veins  or  little 
ridges  extending 
through  the  leaf  from 
the  leaf  stem  vary  (Fig. 
95.)  Sometimes  these 
veins  extend  parallel  to 
each  other  through  the 
leaf,  as  in  the  corn  and 
palm.  This  is  generally 
characteristic  of  mono- 
cotyledonous  leaves.  In 
other  leaves,  the  veins 
form  a  network,  as  in  the  maple  and  apple.  This  is  charac- 
teristic of  dicotyledonous  plants. 

Experiment  99.  —  Place  the  freshly  cut  stem  of  a  white  rose,  white 
carnation,  variegated  geranium  leaf,  or  any  thrifty  leaf  which  is  some- 
what transparent,  in  a  beaker  containing  slightly  warmed  water 
strongly  colored  with  eosin.  Allow  it  to  remain  for  some  time.  The 
coloring  matter  can  be  seen  to  have  passed  up  the  stem  and  spread 
through  the  leaf  or  flower. 


Fig.  95. 


196  FIRST   TEAR   SCIENCE 

'    '  •  f* 

The  great  function  of  the  leaf  is  to  manufacture  plant 

foods.  The  leaf  is  so  constructed  that  air  can  enter  it 
and  come  in  contact  with  its  living  cells,  as  does  the  water 
coming  up  from  its  roots.  The  circulation  of  water  in 
the  leaf  was  seen  in  Experiment  99.  There  is  in  the 
living  cell  of  the  leaf  a  green  substance  called  chlorophyll. 
This  has  the  power  to  utilize  the  energy  of  sunlight  and 
to  combine  carbon  dioxide,  a  gas  which  makes  up  a  small 
part  of  the  air,  with  water  from  the  roots,  forming  a  sub- 
stance which  probably  at  first  is  grape  sugar,  but  which  in 
many  leaves  is  changed  at  once  into  starch. 

Experiment  100.  —  Boil  a  few  fresh  bean  or  geranium  leaves  for  a 
few  minutes  in  a  beaker  of  water.  Pour  off  the  water  and  pour  on 
enough  alcohol  to  cover  the  leaves.  Warm  the  alcohol  by  putting  the 
beaker  in  a  dish  of  hot  water.  When  the  leaves  have  become  color- 
less, remove  from  the  alcohol  and  wash.  Place  the  leaves  in  another 
beaker  and  pour  on  a  solution  of  iodine.  (This  solution  can  be  made 
by  dissolving  in  500  cc.  of  water,  2  grams  of  potassium  iodide  and  | 
gram  of  iodine.  The  solution  should  be  bottled  and  kept.)  If  the 
leaves  turn  dark  blue  or  blackish,  starch  is  present. 

Experiment  101.  —  Place  a  thrifty  geranium  or  other  green  plant 
in  darkness  for  two  or  three  days  and  then  treat  the  leaves  as  was 
done  in  Experiment  100.  Do  they  show  the  presence  of  starch? 
The  direct  presence  of  the  sun's  energy  in  the  form  of  light  is  neces- 
sary for  the  formation  of  starch  in  the  leaves. 

It  was  found  in  Experiment  100  that  leaves  exposed  to 
the  sun  contained  starch,  and  in  Experiment  101  that 
leaves  which  had  been  deprived  of  sunlight  did  not  have 
starch.  The  starch  disappeared  while  the  plant  was  in 
darkness.  Carbon  dioxide  is  composed  of  carbon  and 
oxygen ;  and  water  of  hydrogen  and  oxygen.  In  the 
manufacture  of  starch  by  the  chlorophyll  some  of  the 
oxygen  is  not  used  and  becomes  a  waste  product  which 
the  leaves  throw  off.  This  is  seen  in  Experiment  102. 


PLANT  LEAVES  197 

Experiment  102.  —  Under  an  inverted  funnel  in  a  battery  jar,  place 
some  pond  scum  or  hornwort.  Fill  the  jar  with  fresh  water  and  over 
the  neck  of  the  funnel  place  an  inverted  test  tube  filled  with  water. 
When  placed  in  the  sunlight,  bubbles  of  oxygen  will 
rise  into  the  test  tube  and  collect.  The  oxygen  can  be 
tested  by  turning  the  test  tube  right  side  up  and  quickly 
inserting  a  glowing  splinter.  If  the  splinter  bursts  into 
a  flame,  oxygen  is  present.  (A  freshly  picked  leaf 
covered  with  water  and  put  in  the  sunlight  will  be  seen 
to  give  off  these  bubbles.)  After  a  small  amount  of  gas 
has  been  collected  in  the  test  tube,  mark  the  height  of 
the  water  column  and  place  the  battery  jar  in  the  dark, 
allowing  it  to  remain  there  for  ten  or  ^welve  hours.  No  oxygen  is 
given  off  in  the  dark.  Place  the  jar  in  the  light  again.  Oxygen  is 
given  off.  Is  the  sun's  energy  needed  to  enable  the  plant  to  give  off 
oxygen  ? 

The  starch  manufactured  is  insoluble  in  water  and 
is  stored  in  the  leaf  during  the  day.  But  at  night,  when 
the  leaf  is  not  manufacturing  starch,  it  is  able  to  digest 
the  starch  by  means  of  a  special  substance,  leaf-diastase, 
which  it  forms.  This  changes  it  into  sugar,  which  is 
soluble  and  which  flows  to  other  parts  of  the  plant.  Com- 
pounds such  as  starch  and  sugar,  in  which  there  is  only 
carbon,  hydrogen  and  oxygen,  are  called  carbohydrates. 

The  cells  in  the  leaf  and  in  other  parts  of  the  plant 
have  the  power  to  change  the  sugar  and  combine  it  with 
other  substances  contained  in  the  sap,  thus  forming  more 
complex  chemical  compounds.  These  contain  nitrogen 
and  sulphur,  besides  the  elements  of  the  sugar.  Such 
compounds  are  called  proteins.  They  are  essential  to  the 
formation  of  plant  protoplasm  and  are  very  important  as 
animal  foods. 

The  digested  and  soluble  substances  which  are  prepared 
by  the  leaves  are  transported  to  other  parts  of  the  plant, 
where  they  are  combined  by  the  protoplasm  of  the  living 
cell  with  other  substances  contained  in  the  cell  sap.  Thus 


198 


FIRST   YEAR   SCIENCE 


the  protoplasm  itself  is  able  to  increase  and  form  new  cells 
as  well  as  other  substances,  such  as  woody  tissue  and  oils 
and  resins.  In  forming  these  substances  the  plant  uses 
oxygen  just  as  animals  do.  If  air  is  kept  from  the  roots 
of  certain  plants,  as  was  seen  in  Experiment  94,  the  plants 
cannot  live. 


A  FOREST  OF  PINES. 
From  the  sap  of  these,  turpentine  and  resin  are  made. 

These  food  substances  which  plants  make  by  using  the 
energy  supplied  by  the  sun  are  the  bases  of  all  plant  and 
animal  life.  The  sun's  energy  stored  up  in  the  green  leaf 
is  the  source  of  all  plant  and  animal  energy.  If  it  were 
not  for  the  leaf  manufactory  run  by  the  sun's  power,  life, 
as  we  know  it,  would  cease.  Even  white  plants,  like  the 
mushroom,  must  live  on  the  food  manufactured  by  the 
chlorophyll  of  the  green  plants. 


PLANT  LEAVES 


199 


Fig.  97. 


Experiment  103.  —  Procure  a  small  thrifty  plant  growing  in  a  flower 
pot.  Take  two  straight-edged  pieces  of  cardboard  sufficiently  large 
to  cover  the  top  of  the  flower  pot  and 
notch  the  centers  of  the  edges  so  that 
they  can  be  slipped  over  the  stem  of 
the  plant  and  thus  entirely  cover  the 
top  of  the  flower  pot.  Fasten  the  edges 
of  the  cardboard  together  by  pasting 
on  a  strip  of  paper.  The  top  of  the 
pot  will  now  be  entirely  covered  by  the 
cardboard  but  the  stem  of  the  plant 
will  extend  up  through  the  notches  of 
the  edges.  Cover  the  plant  with  a  bell 
jar.  No  moisture  can  get  into  the  bell 
jar  from  the  soil  in  the  pot  as  it  is 
entirely  covered.  Set  the  plant  thus 
arranged  in  a  warm  sunny  place. 
Moisture  will  collect  on  the  inside  of 
the  bell  jar.  This  must  have  been  given  out  by  the  plant  leaves. 

Since  all  the  processes  of  forming  new  material  by  the 
plant  require  large  amounts  of  water,  it  can  readily  be 

seen  why  water  is  so  essential 
to  plant  development.  The 
water  from  which  the  food 
materials  have  been  taken  is 
thrown  off  by  the  leaves,  as 
seen  in  Experiment  103.  The 
amount  of  water  thus  thrown 
off  by  plants  is  very  great.  A 
single  sunflower  plant  about  six 
feet  tall  gives  from  its  leaves 
about  a  quart  of  water  in  a 
day,  and  an  acre  of  lawn  in  dry 
hot  weather  gives  off  probably 
six  tons  of  water  every  twenty-four  hours. 

If  the  water  passes  out  of  a  plant  too  rapidly  so  that 
there  is  not  enough  left  to  provide  for  the  making  and 


A  SUNFLOWER  PLANT. 


200 


FJRST  TEAR   SCIENCE 


transporting  of  the  food,  the  work  of  the  plant  cannot  be 
carried  on,  and  the  plant  dies.  It  is  on  account  of  this 
that  many  plants  are  especially  prepared*  to  retain  their 
water  supply.  In  almost  all  plants  the  stomata,  or  little 
pores  in  the  leaf  through  which  the  water  passes  out,  close 
up  when  too  much  water  is  being  lost. 

In  some  plants,  like  the  corn,  when  the  root  cannot 
supply  sufficient  moisture,  the  leaves  curl  up  and  thus 

present  less  surface  for  evapora- 
tion. In  trees  like  the  eucalyp- 
tus the  leaves  hang  vertically 
when  the  sun  gets  too  bright 
and  present  their  edges  to  the 
sun's  rays.  Some  leaves,  like 
the  sage,  are  especially  prepared 
to  conserve  their  moisture  by 
having  their  surfaces  covered 
with  hairs.  Others  have  a 
waxy  covering,  as  the  cabbage 
and  the  rubber  tree.  In  some 
plants  the  leaves  are  very  small 
and  have  few  pores,  as  the 
greasewood  of  the  desert,  and  some  have  done  away  with 
leaves  altogether,  as  the  cactus.  It  is  because  the  roots 
cannot  supply  sufficient  moisture  where  the  ground  freezes 
in  the  winter  that  trees  having  large  leaves  shed  them,  and 
only  trees  like  the  pine  whose  needle-like,  waxy  leaves  give 
off  almost  no  moisture  can  retain  theirs. 

95,  Flowers.  —  The  stem  not  only  bears  leaves  but,  in 
the  higher  kinds  of  plants,  it  bears  flowers.  The  function 
of  the  flower  is  to  produce  seeds  and  provide  for  the  con- 
tinued existence  of  its  kind.  If  the  flower  of  a  buttercup, 
quince,  cassia,  or  geranium  is  examined,  it  will  be  found  to 
be  made  up  of  four  distinct  kinds  of  structures. 


EUCALYPTUS  LEAVES. 


FLOWERS 


201 


FLOWER,  SHOWING  COROLLA,  STAMEN 
AND  PISTIL. 


Around  the   outside   is   a   cluster   of   greenish  leaves. 

This  is  called  the  calyx.     Within  the  calyx  is  the  corolla, 

a  cluster  of   leaves  which  in   many  plants   are    colored. 

Within  the  corolla  are 

a  number  of  parts  con- 
sisting of  a  rather  slender 

stalk  with  an  enlarged 

tip.     This  tip  is  called 

the  anther,  and  the  stalk 

and  anther  together,  the 

stamen. 

In  the  center  of  the 

flower,  are    the   pistils. 

At  the  top  of  a  pistil  is 

generally    a    somewhat 

enlarged  portion,  the  stigma,  which  is  sticky  or  rough  ; 

and  at  the  bottom  there  is  an  enlarged  hollow  portion,  the 

seed-bearing  part,  called  the  ovary.     These  two  parts  are 

connected  by  the  stalk- 
like  style.  The  stamens 
and  pistils  are  the  essen- 
tial parts  of  the  flower, 
the  calyx  and  corolla  be- 
ing simply  for  protec- 
tion or  assistance.  All 
flowers  do  not  have  these 
four  parts,  but  every 
flower  has  either  stamen 
or  pistils  or  both. 

The  anther  produces  a 
large    number    of    little 

granular  bodies,  called  pollen  grains,  each  of  which  consists 

of  a  free  cell  containing  protoplasm.     When  the  pollen 

grains  are  ripe,  the  anther  opens  and  exposes  them.     If  a 


PINK  GENTIAN. 

Showing  the  anthers  which  are  covered 
with  pollen . 


202 


FIRST   YEAR   SCIENCE 


pollen  grain  of  the  right  kind  falls  upon  a  stigma,  it  grows 
and  sends  down  a  tiny  tube  through  the  style  into  the 
ovary,  where  a  little  protoplasmic  cell,  called  the  egg  cell, 
has  been  produced.  The  essential  parts  of  these  two  differ- 
ent kinds  of  protoplasms  unite  and  a  new  cell  is  formed. 

This  new  cell  grows  and  divides  into  more  cells,  thus 
forming  the  young  embryo  of  a  new  plant.  This  embryo 
is  the  living  part  of  the  seed  and  around  it  usually  a  great 
deal  of  plant  food  is  stored,  so  that  when  it  begins  to  grow  it 
will  have  plenty  of  nourishment  until  it  is  able  to  develop 
the  roots  and  leaves  necessary  to  prepare  its  own  food. 

Embryos  cannot  be  produced  unless  pollen  grains  and 
egg  cells  unite,  so  it  is  absolutely  essential  that  the  right 

kind  of  pollen  grains  be  brought 
to  the  stigma.  Some  stigmas 
are  able  to  use  the  pollen  grains 
produced  by  the  anthers  of  their 
own  flowers,  but  others  can  only 
use  pollen  from  other  flowers 
and  other  plants.  It  is  there- 
fore necessary  that  these  pollen 
grains  be  carried  about  from 
flower  to  flower  if  fertile  seeds 
are  to  be  produced. 

In  some  cases  the  pollen  is 
borne  about  by  the  wind,  as  in 
the  case  of  corn.  In  this  way  an  exceedingly  large  number 
of  pollen  grains  are  wasted,  as  can  be  seen  by  the  great 
amount  of  yellow  pollen  scattered  over  the  ground  of  a 
cornfield  when  the  corn  is  in  bloom.  In  the  corn  each 
one  of  the  corn  silks  is  a  pistil  and  a  seed  is  produced  at 
its  base  if  a  pollen  grain  lights  upon  the  stigma  at  its  up- 
per extremity.  The  flowers  of  walnut  arid  apple  trees 
are  fertilized  by  wind-blown  pollen. 


MINT  FLOWER. 


FLOWERS  203 

The  pollen  of  very  many  plants,  however,  is  carried 
about  by  humming  birds,  bees  and  other  insects.  As 
the  bee  crawls  into  the  flower  to  get  the 
nectar  at  the  bottom,  it  brushes  against 
the  anther  and  some  of  the  pollen  grains 
become  attached  to  it.  These,  later,  are 
rubbed  off  by  the  rough  or  sticky  stigma 
of  another  flower  which  the  bee  has  en- 
tered and  thus  the  flower  is  fertilized. 
The  humming  bird,  by  reaching  its  long 
slender  beak  down  into  the  long  narrow 
tube  formed  by  the  corolla  of  the  "  wild 
honeysuckle"  (Fig.  98),  brushes  upon 
the  stigma  the  pollen  grains  it  has  ob- 
tained from  another  flower  and  thus  dis- 
tributes pollen  from  flower  to  flower. 
In  no  other  way  could  these  plants  be  fertilized. 

The  beautiful  colors  of  flowers  and  the  sweet  nectars 
that  many  of  them  secrete  are  the  adaptations  of  the  plant 
for  enticing  insects  to  enter  them  and  bring  to  their 
stigma  the  pollen  from  other  flowers,  or  take  from  their 
anthers  pollen  needed  to  fertilize  another  similar  plant. 

Some  flowers  are  so  constructed  that  only  certain  insects 
can  fertilize  them,  the  wild  honeysuckle  requires  the  hum- 
ming bird,  the  red  clover  the  bumble-bee 
(Fig.  99)  and  other  plants,  other  kinds  of  in- 
sects. Flowers  of  some  varieties  of  plants 
cannot  be  fertilized  by  flowers  of  a  like 
variety.  Certain  varieties  of  strawberries, 
for  example,  need  to  have  other  varieties  planted  near 
them,  if  they  are  to  prosper.  Some  plants  need  not  only 
to  have  other  varieties  planted  near,  but  they  also  require 
the  presence  of  special  insects. 

One  of  the  most  striking  examples  of  this  is  the  Smyrna 


204 


FIRST   YEAR   SCIENCE 


fig.  For  many  years  attempts  were  made  to  introduce 
this  fig  into  California.  The  trees  grew  all  right  but 
the  fruit  did  not  mature.  It  was  then  -observed  that  in 
the  regions  where  this  fig  was  successfully  grown  a  species 
of  wild  fig  was  abundant  and  that  the  natives  were  accus- 
tomed to  hang  branches 
of  the  wild  fig  in  the 
Smyrna  fig  trees  at  the 
time  they  were  in  flower. 
These  wild  fig  trees  were 
brought  to  California  and 
grown  near  the  Smyrna 
fig  trees,  but  still  figs  did 
not  mature.  Upon  fur- 
ther examination  it  was 
observed  that  at  the  time 
of  flowering  a  small  insect 
issued  from  the  wild  figs 
and  visited  the  flowers  of 
the  Smyrna  figs.  This 
insect  was  brought  to 
California  and  now  it  is 
possible  to  grow  figs. 
The  flower  of  the  Smyrna 
fig  has  no  stamen  and  it 
is  necessary  for  the  wild 
fig  to  furnish  the  pollen 
which  is  only  successfully  carried  to  the  stigmas  of  the 
edible  fig  by  the  small  fig-fertilizing  insect. 

A  somewhat  similar  case  is  that  of  the  yucca  found  in 
the  dry  region  of  southwestern  United  States.  This 
flower  can  only  be  fertilized  by  the  aid  of  a  small  moth 
which  flies  about  at  night  from  flower  to  flower.  It 
enters  the  flower,  descends  to  the  bottom,  stings  one  of 


YUCCA  OR  SPANISH  BAYONET. 


SEED   DISPERSAL 


205 


the  ovaries,  deposits  an  egg,  then  ascends  and  crowds 
some  pollen  on  the  stigma.  The  grub,  when  it  hatches 
from  the  egg,  feeds  on  the  seeds  in  the  ovary,  but  as  there 
are  many  seeds  in  the  flower  which  have  been  fertilized 
and  the  grubs  eat  only  a  few  of  these,  the  moth  has  made 
it  possible  for  the  yucca  to  produce  seeds  sufficient  for  its 
continued  propagation,  which  would  be  impossible  if  it 
were  not  for  the  moth. 

These  are  only  a  few  of  the  vast  number  of  cases  which 
show  the  close  relationship  existing  between  plants  and 
animals  and  the  dependence  of  the  one  upon  the  other. 

96,  Seed  Dispersal.  —  Not  only  must  flowers  produce  fer- 
tile seeds,  if  the  plants  are  to  continue  to  exist,  but 
these  seeds  must  be  scattered.  To  do 
this  the  seed  pods  of  some  plants  sud- 
denly snap  open  and  spread  their  seeds. 
The  touch-me-not  and  pea  are  examples 
of  this.  In  some  plants,  like  the  maple, 
the  seeds  are  winged  (Fig.  100)  and  float 

for  some  distance  in  the 
Others,  like  the  thistle  and 
dandelion,  have  light  hairlike  ap- 
pendages which  enable  them  to 
float  away.  In  the  case  of  the 
tumble-weed  (Fig.  101)  the  plant 
itself  is  blown  about,  scattering 
the  seeds  over  the  fields  as  it 
bumps  along  from  place  to  place. 

Some  seeds  are  provided  with  hooks  or  barbs,  like  the 
beggar's  ticks  (Fig.  100),  which  attach  the  seeds  to 
animals  so  that  they  are  carried  to  a  distance.  Seeds 
having  an  edible  fruit  cover,  such  as  the  cherry,  black- 
berry and  plum,  are  eaten  by  birds  and  animals  and  the 
undigested  seed  deposited  far  away  from  the  place  where 


Fig.  100. 


air. 
the 


Fig.   101. 


206 


FIRST   YEAE   SCIENCE 


SCRUB  OAK  BRANCH. 
Showing  the  acorns. 


the  seed  grew.     Seeds  like  the  acorn  are  carried  about  by 
squirrels  and  other  animals.     Many  seeds  are  able  to  float 

in  water  for  a  considerable  time 
without  being  injured  and  are 
borne  about  by  currents.  Shores 
of  streams  and  islands  receive 
many  of  their  plant  seeds  in 
this  way.  The  cocoanut  palm 
is  a  notable  seed  of  this  kind 
and  is  found  widely  scattered 
over  tropical  islands. 

97.  Seeds  and  their  Germination. 
— Experiment  104.  —  Take  two  com- 
mon dinner  plates  and  place  in  the 
bottom  of  one  of  them  two  or  three 
layers  of  blotting  paper  and  thoroughly 
wet  it.  Place  some  wheat  or  other  kinds  of  seeds  upon  this.  Now 
invert  the  other  plate  over  the  first,  being  careful  to  have  the  edges 
touch  evenly.  This  makes  a  moist  chamber  and  gives  the  most  favor- 
able conditions  for  germination.  Do  all  the  seeds  germinate  at  the 
same  time?  Does  the  position  of  the  seed  make  any  difference? 
What  takes  place  first  in  the  process  of  germination  ?  What  appears 
first,  the  leaf  or  the  root?  Why  does  the  seed  shrivel  up? 

Experiment  106.  —  Cut  open  several  seeds,  such  as  pumpkin,  squash, 
bean,  corn,  and  drop  on  to  the  inside  of  each  a  few  drops  of  the  iodine 
solution  made  in  Experiment  100.  Do  the  seeds  show  the  presence  of 
starch  ? 

Experiment  106.  —  Soak  some  beans  for  about  twenty-four  hours. 
Rub  off  the  skin  from  two  or  three  and  examine  their  different  parts 
carefully.  Plant  the  beans  in  a  box  of  damp  sawdust.  Put  the  box 
in  a  warm  place.  Plant  some  corn  that  has  been  soaked  for  two  or 
three  days  in  the  same  box.  After  the  seeds  have  been  planted  sev- 
eral days,  carefully  remove  a  bean  and  a  grain  of  corn  and  examine. 
Make  a  sketch  of  each  of  the  seeds. 

After  a  few  days  more  remove  another  seed  of  each  and  examine 
and  sketch.  Continue  to  do  this  until  the  little  plants  have  become 
quite  well  grown.  Do  the  two  seeds  develop  alike?  Which  of  the 


SEEDS  AND   THEIR   GERMINATION  207 

seeds  has  two  similar  parts?  These  two  parts  are  called  cotyledons. 
What  appears  to  be  the  use  of  these  parts  to  the  sprout?  Consult 
the  results  of  Experiment  104.  Note  the  root  development  in  each 
seed  and  the  stem  development.  The  sprouts  get  their  food  from  the 
seed. 

When  we  examined  the  different  seeds  in  Experiment 
105,  we  found  that  they  each  contained  starch.  When 
the  seeds  were  soaked  and  planted,  we 
found  that  a  part  of  the  seeds  began  to 
grow,  forming  a  sprout.  This  part  is  the 
embryo  already  described.  We  also  saw 
that  the  bean  seed  divided  into  two 
like  parts  which  gradually  withered  and 
shrank,  as  the  sprout  grew,  while  the 
corn  had  only  one  such  part. 

These  parts  are  called  cotyledons,  or 
seed  leaves  (Fig.  102).  The  bean  seed 
is  a  dicotyledon  (two  seed  leaves)  and 
the  corn  a  monocotyledon  (one  seed  leaf). 
These  cotyledons  are  the  food  storehouses 
for  the  germinating  seed.  As  the  sprout 
grew,  the  root,  with  its  root  hairs,  developed,  and  the 
stem  with  its  leaves.  When  these  had  grown  strong 
enough,  the  cotyledons,  having  performed  their  part, 
dropped  off.  The  plant  was  now  ready  to  prepare  its 
own  food  by  the  aid  of  the  sunlight. 

Experiment  107.  —  Place  several  beans  in  a  tumbler  of  damp  saw- 
dust and  put  it  in  a  warm,  light  place.  Keep  the  sawdust  moistened. 
After  the  beans  are  well  sprouted,  with  a  sharp  knife  cut  one  of  the 
half  beans  or  cotyledons  off  from  a  sprout.  .  Cut  both  cotyledons  off 
another  sprout.  Put  the  sprouts  back  on  the  sawdust.  Do  the 
sprouts  grow  as  well  as  those  of  the  other  beans  ? 

Experiment  108.  —  Fill  a  16-ounce  wide-mouth  bottle  about  one 
third  full  of  peas  or  beans.  Pour  in  water  enough  to  more  than  cover 
them.  Tightly  cork  the  bottle  and  put  in  a  warm  sunny  place.  Put 


208  FIRST   YEAR   SCIENCE 

'  .  ** 

another  similar  corked  empty  bottle  beside  it.  Allow  the  bottles  to 
stand  for  several  days  until  the  peas  have  sprouted.  Remove  the  cork 
from  the  bottle  containing  the  peas  and  insert  a  biirning  splinter.  Do 
the  same  to  the  empty  bottle.  Why  does  not  the  splinter  burn  as  well 
in  each?  If  on  being  placed  in  either  bottle  the  splinter  is  smothered 
out,  it  shows  the  presence  of  carbon  dioxide. 

Experiment  109.  —  Fill  two  8-ounce  wide-mouth  bottles  each  about 
one  third  full  of  coarse  sawdust  and  fill  the  remaining  part  with  peas 
which  have  been  soaked  for  a  day.  Pour  in  sufficient  water  to  cover  the 
sawdust.  Cork  one  of  the  bottles  tightly,  leaving  the  other  open. 
Put  the  two  bottles  in  a  warm  sunny  place.  Whenever  necessary, 
pour  on  sufficient  water  to  keep  the  sawdust  in  the  open  bottle  wet. 
In  which  bottle  do  the  seeds  sprout  the  better  ?  Does  air  appear  to 
be  necessary  for  the  growth  of  seeds  ?  As  determined  by  the  previous 
experiment,  what  part  of  the  air  is  used  ? 

We  found  in  Experiment  107  that  if  the  cotyledons 
were  cut  off  before  the  sprout  had  become  sufficiently 
mature,  it  could  not  continue  its  growth.  In  Experiment 
108  we  found  that  the  sprouting  seeds  took  up  oxygen 
from  the  air  and  gave  out  carbon  dioxide  just  as  animals 
do.  Energy  was  needed  and  this  energy  was  obtained  by 
combining  the  carbon  in  the  seed  with  the  oxygen  in  the 
air,  as  it  is  when  wood  is  burned.  We  found  in  Experi- 
ment 109  that  the  seeds  could  not  sprout  well  unless  suffi- 
cient air  was  supplied.  That  was  because  there  was  not 
enough  oxygen  supplied  to  furnish  the  necessary  energy. 

Experiment  110.  —  Place  several  sprouted  seeds  in  each  of  two 
tumblers  nearly  filled  with  damp  sawdust.  Put  these  tumblers  side 
by  side  in  a  warm  light  place.  Cover  one  of  the  tumblers  with  a  box 
painted  black  so  as  to  exclude  the  light.  In  which  do  the  seeds  grow 
the  better  ? 

After  the  seeds  were  sprouted  and  had  begun  to  pre- 
pare their  own  food,  it  was  found  in  Experiment  110  that 
they  were  not  able  to  do  this  unless  exposed  to  the  light 
of  the  sun.  The  parent  plant  had  stored,  in  a  latent  form 
in  the  seed,  energy  which  it  had  received  from  the  sun. 


FUNGI  209 

This  potential  energy  the  sprout  was  able  to  change  into 
the  kinetic  form  by  the  aid  of  oxygen,  and  to  use  in  the 
work  of  growing.  After  this  latent  energy  had  been  ex- 
pended, it  had  to  fall  back  upon  the  direct  energy  of  the 
sun  which  came  to  it  in  the  form  of  sunlight. 

98.  Fungi.  — Experiment  111.  —  Expose  a  piece  of  moist  bread 
to  the  air  for  a  short  time  and  then  put  it  into  a  covered  dish  so  as  to 
retain  the  moisture.  Does  any  change  take  place  in  the  bread?  Ex- 
amine with  a  magnifying  glass  the  mold  which  appears. 

Experiment  112.  —  (1)  Bruise  a  sound  apple  and  place  the  bruised 
part  in  contact  with  a  thoroughly  rotten  apple.  Wrap  the  two  up  to- 
gether in  a  wet  cloth  and  put  in  a  fruit  jar.  Seal  the  jar  to  prevent 
the  water  from  evaporating.  (2)  Plunge  a  pin  repeatedly  first  into  a 
rotten  apple  and  then  into  a  sound  one.  Wrap  the  sound  apple  in  a 
wet  cloth  and  seal  in  a  fruit  jar.  (3)  Place  a  lemon  which  has  de- 
veloped a  green,  spongy,  rotten  place  in  it  in  contact  with  a  perfect 
lemon  and  keep  them  where  they  will  be  moist.  What  happens 
to  the  sound  fruits  ? 

The  plants  that  we  have  so  far  studied  are  green  plants 
and  contain  chlorophyll.  They  are  able  to  prepare  their 
food  from  the  air  and  soil  by  the  aid  of  the  sun's  energy. 
There  is,  however,  another  great  group  of  plants  which 
have  no  chlorophyll  and  which  are  obliged  to  live  upon  the 
food  that  green  plants  have  prepared.  They  find  this  food 
either  in  the  living  or  in  the  dead  parts  of  plants  or  animals, 
the  animals  having  digested  it  from  plants  or  other  animals 
who  originally  obtained  it  from  plants. 

Plants  that  have  no  chlorophyll  and  live  upon  the  food 
green  plants  have  prepared  are  called  fungi.  The  bacteria 
belong  to  this  group.  If  plants  live  upon  living  plants  or 
animals,  they  are  called  parasites,  if  upon  dead  ones,  sapro- 
phytes. Plants  of  this  kind  are  exceedingly  important, 
although  many  of  them  can  be  seen  only  with  the  micro- 
scope. Without  them  the  earth  would  soon  become  unin- 


210 


FIRST  YEAR   SCIENCE 


habitable.     Some    of   them    are  injurious  to   plants   and 
animals,  but  a  large  number  are  most  beneficial. 

These  plants  cause  the  decay  of  dead  a'nimal  and  vege 
table  matter.  If  it  were  not  for  them,  all  the  plants  and 
animals  that  die  upon  the  earth  \\ould  encumber  its  surface 
indefinitely  with  their  bodies,  and  none  of  the  material 
that  they  have  taken  from  the  soil  would  return  to  fertilize 

it.  These  plants  make 
possible  the  manufacture 
of  vinegar,  some  cheeses 
and  a  great  many  other 
things  which  we  use 
daily. 

On  the  other  hand,  the 
decay  in  fruit,  the  mold 
on  bread,  the  corn  smut, 
the  smut  on  oats  and 
barley,  the  potato  blight, 
the  scabs  of  apples  and 
potatoes,  the  rusts  on 
grains  and  many  other 
common  plant  diseases 
are  simply  fungus  plant 
growths.  The  wheat  rust 
alone  costs  the  United 
States  many  millions  of  dollars  each  year.  Thousands  of 
feet  of  timber  are  destroyed  yearly  by  the  wood -destroy  ing 
fungi.  Dry  rot  of  timber,  as  it  is  called,  is  due  to  a  fun- 
gus growth.  The  fight  against  these  harmful  fungi  costs 
millions  of  dollars  each  year. 

But  some  fungi  are  exceedingly  useful.  The  fungus 
most  commonly  made  use  of  is  the  yeast  plant.  In  bread 
making,  yeast  which  contains  the  little  yeast  plants  is 
mixed  thoroughly  into  the  material  which  is  to  compose 


MISTLETOE  GROWING  ON  AN  OAK. 
An  interesting  parasitic  plant. 


FUNGI  211 

the  bread,  and  the  bread  is  then  put  into  a  warm  place  to 
rise  or,  more  exactly,  to  grow  yeast  plants.  If  the  mate- 
rials and  the  temperature  are  right,  the  yeast  plants  grow 
very  rapidly,  feeding  upon  the  material  of  the  dough  and 
changing  the  sugar  into  carbon  dioxide  and  alcohol. 
Little  bubbles  of  gas  are  developed  throughout  the  dough, 
making  it  slightly  porous. 

The  bread  is  then  kneaded  to  mix  the  greatly  increased 
number  of  yeast  plants  still  more  thoroughly  and  is  allowed 
"to  rise"  again.  The  plants  are  by  this  time  very  uni- 
formly scattered  through  the  dough  and  they  develop  little 
bubbles  of  carbon  dioxide  throughout  the  mass  so  that  a 
light  sponge  results.  When  this  is  heated  in  the  oven, 
the  tiny  bubbles  of  gas  expand,  making  a  more  porous 
sponge,  the  alcohol  evaporates,  and  the  dough  hardens,  thus 
forming  light  bread.  Although  the  study  of  these  minute 
fungi  is  very  interesting,  it  must  be  done  by  aid  of  the 
microscope  and  will  not  be  attempted  here. 

We  are  most  of  us  familiar  with  some  of  the  larger 
fungi  such  as  the  mushrooms  (Fig.  103)  and  toadstools. 
Mushrooms  are  widely  used  as  a  delicacy 
and  their  growth  is  an  important  indus- 
try in  some  sections.     They  are  grown  in 
soils  very  rich  in  humus  and  generally 
in  dark,  cellar-like  places.     The  mush- 
rooms that  grow  wild  in  the  woods  are 
abundant  in  some  localities  but  should 
not  be  used  for  food  unless  most  care-  Fi     103 

fully  examined  by  some  one  who  is 
expert  in  determining  the  different  species.  There  are 
several  species  of  mushrooms  which  are  exceedingly  poison- 
ous. For  one  of  these  there  is  no  known  antidote.  The 
general  structure  of  these  larger  fungi  can  be  seen  by 
examining  a  mushroom  obtained  from  the  market. 


212 


FIRST   YEAR   SCIENCE 


Experiment  113.  — Place  a  slice  of  freshly  boiled  potato  in  each 
of  five  clean  4-ounce  wide-mouth  bottles.  Close  the  mouths  of  the 
bottles  with  loose  wads  of  absorbent  cotton.  Place  four  of  these 
bottles  in  a  sterilizer  and  sterilize  for  half  an  hour.  Allow  one  bottle 
to  remain  unsterilized.  (A  sterilizer  can  be  made  by  taking  a  covered 

tin    pail    and    putting    into 

the  bottom  of  it  a  bent  piece 
of  tin  with  holes  punched  in 
it  to  act  as  a  shelf  on  which 
to  put  the  bottles.  A  shallow 
tin  dish  with  holes  in  it  is 
good  for  the  shelf.  There 
must  be  holes  so  that  the 
steam  will  not  get  under  the 
shelf  and  upset  it.  Fill  the 
sterilizer  with  water  to  the 
top  of  the  shelf  and  place 
the  bottles  on  the  shelf.  Keep 
the  water  boiling.)  A  reli- 
able inexpensive  sterilizer  is 
the  pressure  cooker  shown  in 
Figure  104. 

Take  the  bottles  out  and 
allow  them  to  cool.  Remove  the  cotton  from  one  of  them  for  several 
minutes  and  then  replace.  Run  a  hat  pin  two  or  three  times 
through  the  flame  of  a  Bunsen  burner  to  sterilize  it  and  place 
it  in  the  water  of  a  vase  which  has  had  flowers  in  it  for  some 
time.  Carefully  pulling  aside  the  edge  of  the  absorbent-cotton 
stopper  in  the  second  bottle,  insert  the  pin  and  place  a  drop  of  the 
vase  water  on  the  surface  of  the  piece  of  potato.  After  having  steri- 
lized the  pin  again,  rub  it  several  times  over  the  moistened  palm  of 
the  hand  and  then,  using  the  same  precautions  as  before,  scratch  the 
potato  in  the  third  bottle.  Keep  the  fourth  bottle  just  as  it  was  taken 
from  the  sterilizer,  as  an  indicator,  that  is,  to  see  whether  the  bottles 
were  thoroughly  sterilized.  Put  all  of  the  bottles  away  in  a  warm 
place  and  observe  them  each  day  for  several  days.  The  spots  appear- 
ing on  the  pieces  of  potato  are  bacteria  colonies. 

99.  Bacteria.  —  The  nitrogen-fixing  bacteria  were  consid- 
ered, to  some  extent,  under  soil,  but,  as  these  soil  bacteria 


Fig.   104. 


BACTERIA  213 

are  but  few  in  comparison  with  the  great  number  of  species 
found  existing  almost  everywhere  upon  the  earth's  surface, 
bacteria  will  be  further  considered  here.  In  Experiment 
113  we  found  that  if  substances  are  left  exposed  to  the  air 
they  soon  undergo  certain  changes,  which  they  are  free 
from  when  properly  protected.  These  changes  are  due  to 
bacteria. 

The  bacterium  is  a  single-cell  plant,  probably  the  simplest 
of  all  plants  ;  it  can  only  be  seen  with  a  high-power  micro- 
scope.       Bacteria     are     rod-shaped, 
thread-shaped,  screw-shaped  or  have 
various  other  forms  (Fig.  105).     The 
protoplasm  in  the  cell  of  bacteria  has 
the   power   to   assimilate    food    and 
build  more  protoplasm.     When  the 
cell  has  grown  sufficiently,  it  divides 
into  two  cells. 

A   healthy   bacterium    grows   fast         *  ^ 
enough  to  be  ready  to  divide  about  **  . 

once   an    hour.     If   it    divided   once        *~^ 
an  hour  and  each  division  continued 
to  divide  once  an  hour,  in  the  course  p.      1Q5 

of  twenty-four  hours  there  would  be 

nearly  seventeen  million  bacteria  produced.  If  this  were 
kept  up  for  some  weeks,  the  mass  of  bacteria  would  be  as 
large  as  the  earth.  Of  course,  this  would  mean  that  each 
bacterium  had  plenty  of  room  to  live  in  and  plenty  of 
food  to  live  on  and  nothing  to  injure  it.  These  con- 
ditions are  not  found,  and  each  bacterium  has  to  struggle 
for  existence  just  as  every  other  plant  does.  As  it  is, 
however,  bacteria  are  numberless. 

Since  bacteria  and  fungi  cause  the  "  spoiling  "  of  food, 
it  is  necessary  to  find  means  of  stopping  their  growth.  It 
has  been  found  that  thoroughly  smoking  fish  and  meat 


214 


FIRST   TEAR   SCIENCE 


preserves  it ;  that  salt  acts  as  a  preservative  ;  that  if  fruit 
is  heated  to  a  boiling  temperature  and  tightly  sealed  in 
cans  it  will  keep,  and  that  fruits  do  not  spoil  if  placed  in 
strong  sugar  sirups. 

These  and  many  other  methods  are  used  to  keep  bacteria 
away  from  food  and  to  prepare  the  food  in  such  a  way  that 
bacteria  cannot  live  in  it.  It  is  found  that  bacteria  do  not 


PREPARING  SMOKED  FISH  AT  GLOUCESTER. 

thrive  as  well  if  placed  where  it  is  cold,  so  foods  are  kept 
in  cold  places.  Many  bacteria  cannot  stand  the  sunlight; 
that  is  one  of  the  reasons  why  it  is  so  much  more  healthful 
to  live  in  sunny  rooms. 

Steam  is  sufficient  to  kill  bacteria  as  they  usually 
exist.  Under  some  conditions  they  can,  however,  with- 
stand a  greater  temperature  than  that  required  to  boil 
water.  We  found  that  they  did  not  pass  through  ab- 


BACTERIA  215 

sorbent  cotton.  It  has  been  discovered  that  certain 
substances,  like  formaldehyde  and  hydrogen  peroxide, 
prevent  their  growth.  These  substances  are  called 
disinfectants. 

Certain  bacteria  thrive  in  the  living  flesh  ;  it  is  therefore 
necessary  to  disinfect  cuts  or  else  blood  poisoning,  which 
is  a  bacterial  disease,  may  set  in.  Sometimes  when  a  rusty 
nail  is  run  into  the  hand  or  foot,  if  the  wound  is  not 
properly  disinfected  and  cared  for,  lockjaw,  another  bac- 
terial disease,  is  developed.  After  a  wound  is  disinfected, 
it  is  usually  dressed  with  absorbent  cotton  in  order  to  keep 
out  the  bacteria. 

Bacteria  are  the  cause  of  many  diseases,  such  as  pneu- 
monia, tuberculosis,  smallpox,  typhoid  fever  and  others. 
People  having  diseases  of  these  kinds  throw  off  great 
quantities  of  bacteria,  usually  called  germs.  If  such  germs 
are  breathed  into  the  lungs  or  swallowed  into  the  stomach 
and  intestines  of  other  people,  they  give  them  these  dis- 
eases. It  is  necessary,  therefore,  in  diseases  of  this  kind 
to  take  every  precaution  that  the  germs  shall  not  be  scat- 
tered abroad. 

Tuberculous  patients  should  be  exceedingly  careful  to 
use  individual  dishes,  to  cover  their  mouths  with  cloths 
when  sneezing  or  coughing,  otherwise  they  will  scatter 
vast  numbers  of  disease  germs  and  become  a  menace  to 
society.  Although  thousands  are  afflicted  each  year  with 
tuberculosis,  largely  through  the  carelessness  of  those 
having  the  disease,  it  is  a  readily  preventable  and  curable 
disease.  The  vile  and  dangerous  habit  of  spitting  should 
be  abolished  everywhere  and  public  drinking  cups  and 
towels  should  be  abolished. 

When  diseases  are  very  virulent,  like  smallpox  or  diph- 
theria, the  patients  are  usually  kept  by  themselves,  quaran- 
tined, their  rooms  kept  disinfected  and  every  precaution 


216 


FIRST   YEAR   SCIENCE 


taken  that  people  who  are  susceptible  to  the  disease  shall 
not  be  exposed  to  the  germs. 

When  disease  bacteria  get  established'  in  the  system, 
they  secrete  a  poison  called  toxin,  which  is  absorbed  by 
the  blood  and  carried  throughout  the  body,  thus  poisoning 
many  other  parts  beside  those  immediately  attacked  by 
the  bacteria.  The  cells  of  the  body  at  once  begin  to  se- 
crete a  substance  to  counteract  this  poison,  an  antitoxin. 
If  the  vitality  of  the  patient  is  great  enough,  sufficient  anti- 
toxin will  be  secreted  to  neutralize  the  effect  of  the  toxin 
and  the  disease  will  be  overcome. 

Of  late  years  it  has  been  found  that  these  antitoxins 
can  be  artificially  supplied  or  caused  to  develop.  Thus 

the  system  may  be  aided  in 
neutralizing  the  effect  of  the 
toxin,  arid  in  warding  off  the 
disease.  By  injecting  these 
antitoxins  or  stimulating  their 
development,  people  are  now 
protected  against  smallpox, 
diphtheria  and  other  diseases. 
Disease  bacteria  are  not  only 
found  in  the  air,  but  also  in 
water  and  milk  and  other  kinds 
of  food.  We  must  therefore 
these  germs  from  our  water, 
Many  cases  of  typhoid  fever 
have  .been  directly  traced  to  the  milk  supplied  by  a 
dealer  in  whose  family  was  a  case  of  the  fever.  Flies  (Fig. 
106)  are  great  carriers  of  bacteria  and,  by  crawling  over 
food,  spread  diseases.  . 

Germs  thrive  particularly  in  sewers,  cesspools  and  un- 
sanitary places,  so  that  these  should  be  especially  watched. 
The  best  guards  against  disease,  however,  are  plenty  of 


106. 


be  very  careful   to   keep 
milk  and   food   supply. 


CLASSIFICATION   OF  ANIMALS  217 

sunshine  and  air,  wholesome  food,  sufficient  rest  and  a 
tranquil  mind.  With  these  aids,  the  body  is  usually  pre- 
pared in  itself  to  kill  the  germs  that  come  into  it.  Every 
day  each  person  probably  receives  into  his  system  thousands 
of  disease  germs  and  usually  it  is  only  when  the  vitality 
of  the  body  is  low  that  these  germs  are  able  to  establish 
themselves.  Right  living  is  the  great  disease  preventer. 

As  has  already  been  stated,  however,  disease  bacteria 
are  only  a  small  portion  of  the  bacteria  group  of  plants 
and  the  usefulness  of  the  other  members  of  this  group  is 
far  greater  than  their  harmfulness.  Science  each  year  is 
becoming  more  and  more  able  to  fight  the  disease  germs, 
but  it  is  entirely  unable  to  supply  the  necessary  aid  given 
by  the  useful  bacteria  to  animals  and  plants  and,  through 
them,  to  man. 

100.  Animals.  —  Animals  do  not  take  their  energy  directly 
from  the  sunlight,  but  indirectly  from  the  latent  energy 
stored  up  in  the  foods  prepared  by  green  plants.     These 
foods  may  be  eaten  as  stored  by  the  plants,  or  they  may 
have  passed  through  the   medium    of   other   plants   and 
animals.     The  energy  thus  stored  up  is  liberated  by  com- 
bining the  carbon  with  oxygen.     Carbon  dioxide  is  freed. 

The  green  plants  use  this  carbon  dioxide  again  and,  by 
the  aid  of  the  sun's  energy,  free  the  oxygen  and  store  up 
the  carbon.  Thus  the  cycle  goes  on,  over  and  over,  the 
plants  freeing  oxygen  and  taking  up  carbon  dioxide,  and 
the  animals  freeing  carbon  dioxide  and  taking  up  oxygen. 
The  cells  of  plants  which  feed  upon  the  food  prepared  by 
the  chlorophyll  of  the  leaves  use  oxygen  and  give  out 
carbon  dioxide  just  as  the  animal  cells  do;  so  also  do  other 
plants  to  some  extent,  but  this  is  in  small  quantities. 

101.  Classification  of  Animals.  —  For  convenience  of  study 
the    animal   kingdom    has   been  divided  into  two   great 
classes  —  the    invertebrates    (without   backbone)  and  the 


218 


FIRST  YEAR  SCIENCE 


vertebrates  (with  backbone).  The  invertebrate  is  the 
much  more  numerous  class  as  it  contains  the  worms,  shell- 
fish, insects  and  those  almost  countless  forms  of  animal 
life  which  have  no  internal  bony  skeleton  and  backbone. 
The  higher  animals,  like  fishes,  amphibia,  reptiles,  birds  and 
mammals,  belong  to  the  class  of  vertebrates.  Man  himself 
is  the  highest  of  the  vertebrates,  and  as  the  purpose  of 
this  book  is  to  study  the  earth  and  its  relation  to  man,  his 
structure  will  be  studied  later. 

102.  Invertebrates ;  Protozoa.  —  The  very  lowest  form  of 
animal  life,  the  protozoa,  are  single-celled  animals.  In  some 
species  they  are  very  difficult  to  distinguish  from  plants. 
They  are  microscopic  in  size  and  most  of  them  live  in 
water.  Our  chief  interest  in  them  in  the  present  study  is 
that  they  are  the  cause  of  several  kinds  of  disease  which 
can  readily  be  prevented  with  proper  care.  Malaria,  and 
the  terrible  African  disease  called  the  sleeping  sickness, 
and  probably  yellow  fever  are  due  to  these  little  animals. 
Unlike  bacteria,  the  protozoa  do  not  cause  disease  by 
passing  directly  from  one  person  to  another,  instead  they 

need   to   live   in   some 

insect  between  whiles. 
In  malaria  and  yellow 
fever  the  insect  in 
which  they  live  is  the 
mosquito,  and  in  the 
sleeping  sickness  they 
live  in  a  fly  called  the 
tsetse.  If  a  mosquito 
of  the  right  species  bites 
a  person  afflicted  with 
malaria  or  yellow  fever, 
some  of  these  little  animals,  the  protozoa,  are  sucked  up  with 
the  blood  and  enter  the  mosquito.  They  grow  in  its  body, 


A  DISEASE-BEARING  MOSQUITO. 
Greatly  magnified. 


72V  VER TEB RA  TES  ;    PROTOZOA 


219 


undergoing  several  changes,  until  the  animal  germs  are 
ready  to  be  injected  into  their  victim,  when  they  pass 
into  the  salivary  glands  of  the  mosquito.  In  biting,  the 
mosquito  always  injects  a  little  saliva  into  the  wound  and 
with  this  go  the  germs.  These  enter  the  blood,  multiply 
rapidly  and  cause  the  disease. 

If  mosquitoes  can  be  kept  from  biting  people  who  have 


A  "MALARIAL"  SWAMP. 
A  breeding  place  for  mosquitoes. 

these  diseases  or  if  infected  mosquitoes  can  be  kept  from 
biting  other  people,  such  diseases  will  not  spread.  The 
best  way  to  keep  mosquitoes  from  biting  is  to  exterminate 
them.  Since  mosquitoes  breed  in  stagnant  water,  all  old 
dishes  or  small  pools  where  water  accumulates  should  be 
emptied  and  drained.  Larger  stagnant  pools  should  be 
drained  or  have  a  film  of  kerosene  spread  over  their  surface 
by  frequently  pouring  a  little  of  the  oil  on  the  water. 


220  FIRST   YEAR   SCIENCE 

1  .  ./* 

This  will  keep  the  mosquitoes  from  breeding  and  prevent 
the  diseases. 

Thus  mosquitoes  and  flies,  the  summer  pests,  are  not 
only  exceedingly  annoying,  but  are  very  likely  to  spread 
disease.  The  Texas  fever  which  has  caused  such  great 
financial  losses  to  the  cattlemen  of  the  United  States  is 
caused  by  a  protozoan  injected  into  the  cattle  by  the  bite 
of  a  tick. 

103.  Worms.  —  Another  class  of  invertebrates  is  the 
worms.  One  of  these,  the  earthworm,  was  found  in  the 


EARTHWORM. 
A  great  helper  of  the  farmer. 

study  of  soilmaking  to  be  very  important  and  should  be 
considered  in  this  place.  If  an  earthworm  is  examined,  it 
will  be  seen  that  the  body  is  made  up  of  segments  or 
rings,  and  that  it  moves  by  successively  shortening  and 
elongating  its  body.  Extending  through  the  middle  of  the 
body  is  an  alimentary  canal  consisting  of  a  mouth,  gizzard 
for  grinding  food,  stomach  and  intestines. 

Near  the  head  is  a  little  nerve  center.  The  whole 
animal  may  be  regarded  as  built  up  by  the  joining  of  a 
number  of  essentially  similar  segments.  A  more  minute 
examination  will  show  that  these  segments  have  been 
materially  modified  in  some  portions  of  the  animal,  but 


INSECTS 


221 


they  have  not  been  in  any  respect  organized,  as  have  the 
different  parts  of  higher  animals.  This  simple  animal, 
as  has  already  been  seen,  is  an  untiring  worker  in  prepar- 
ing and  fertilizing  soil  for  plants,  and  thus  is  a  most 
efficient  helper  to  man. 

104.  Insects.  —  Experiment  114.  —  Procure  a  bumble-bee  or  honey- 
bee, as  a  type  insect,  and  inclose  it  in  a  small  glass-covered  box.  Into 
how  many  parts  is  the  body  divided?  Describe  these  parts.  To 
which  part  are  the  legs  attached?  The  wings?  How  many  legs  are 
there?  How  many  wings?  Notice  the  largest  part  into  which  the 
body  is  divided.  Notice  the  eyes  and  the  feelers,  or  antennce,  on  the 
head.  Write  a  short  description  of  the  general  characteristics  of  the 
bee's  body. 

The  insects  are  among  the  most  important  of  animals. 
This  class  contains  more 
than  half  the  known 
animal  species.  They 
are  spread  widely  over 
all  parts  of  the  earth. 

Both  good  and  bad  in- 
sects abound.  Econom- 
ically, they  furnish  mil- 
lions upon  millions  of 
dollars  worth  of  prod- 
uce every  year  and  on 
the  other  hand  destroy 
hundreds  of  millions  of 
dollars  worth  of  crops 
and  trees.  It  has  been 
estimated  that  in  the 

United  States  insects  de-  F          BuTTERFLIES  ON  ALFAI.FA. 
stroy   every   year   crops 

and  trees  which  have  a  value  of  150,000,000,  to  say 
nothing  of  the  countless  losses  due  to  diseases  spread  by 


222  FIRST   YEAR   SCIENCE 

'  '  •          r* 
flies  and  mosquitoes.     Not  many  years  ago  grasshoppers 

nearly  devastated  several  of  the  middle  western  states. 

The  most  productive  insects  are  the  silk  worms  and  the 
bees.  Without  the  silk  worm  (Fig.  107)  there  would  be 
no  silk  produced,  and  without  the  bee,  no  honey.  These 

two  products  each  year 
run  into  hundreds  of  mil- 
lions of  dollars.  We  have 
already  seen  that  bees  and 
other  insects  are  needed 
also  for  the  fertilization 
of  flowers. 

Among  the  most  inter- 

Fi     jQ7  esting  of  the  insects  and 

perhaps,  everything  con- 
sidered, the  most  valuable,  is  the  honey-bee.  This  is 
the  great  flower  fertilizer;  it  would  fertilize  about  all 
the  plants  man  really  needs  except  the  red  clover. 
In  the  United  States  alone  there  is  produced  by  it  about 
twenty-five  million  dollars  worth  of  honey  and  wax  each 
year. 

In  Experiment  114,  it  was  found  that  the  body  of  the 
bee,  like  other  insects,  is  divided  into  three  parts.  These 
parts  are  called  head,  thorax  and  abdomen.  The  eyes 
and  the  feelers,  or  antennae,  are  on  the  head.  The  mouth 
is  a  very  complex  organ,  fitted  both  for  biting  and  for 
sucking.  The  six  legs  and  four  wings  are  on  the  thorax. 
The  hind  leg  of  each  working  bee  is  so  shaped  and  fringed 
with  hairs  that  it  forms  a  pollen  basket. 

Honey-bees  live  in  large  colonies  and  in  the  colony 
there  are  three  kinds  of  bees,  the  male  bees,  or  drones, 
the  workers  and  the  queen  or  female  bee.  The  workers 
are  the  ones  that  make  all  of  the  honey  and  wax,  do  all  the 
work  of  the  hive  and  feed  the  grubs  on  rich  food  formed 


INSECTS  223 

in  their  own  stomachs,  as  well  as  on  pollen  mixed  with 
honey.  The  grubs  are  the  first  stage  in  the  development 
of  the  bee  from  the  egg.  The  queen  lays  all  the  eggs, 
sometimes  as  many  as  a  million.  There  is  but  one  queen 
in  each  swarm.  "  Whenever  another  queen  is  ready  to  be 
hatched,  the  old  queen  takes  about  half  the  colony  and 
goes  off  to  form  another  swarm. 

The  wax  is  secreted  from  glands  in  the  abdomen  of  the 


BEEHIVES. 
Hundreds  of  dollars  worth  of  honey  are  produced  here  each  year. 

workers  and  with  this  the  bees  build  the  comb.  Each  cell 
is  hexagonal  in  cross  section  and  the  comb  is  so  constructed 
that  the  least  possible  amount  of  wax  will  inclose  the 
greatest  possible  amount  of  honey.  The  nectar  at  the 
bases  of  flowers  supplies  the  bee  with  the  material  from 
which  it  makes  the  honey.  It  is  in  seeking  for  this  that 
the  bee  visits  so  many  flowers  and  scrapes  the  pollen  on  to 
the  different  parts  of  its  body  to  be  borne  away  to  ferti- 
lize other  flowers  which  it  enters.  Such  an  interesting 
animal  and  so  exceedingly  useful  is  the  bee  that  hun- 
dreds of  books  have  been  written  about  it,  more  than  about 


224 


FIRST   YEAR   SCIENCE 


any  other  domestic  animal.    Some  of  these  should  be  read  for 
further  information  concerning  this  most  instructive  animal. 

105.  Vertebrates.  —  Experiment  116.  —  If  possible,  secure  the 
skeleton  of  some  vertebrate  animal,  preferably  man.  Notice  how  the 
bones  are  fitted  to  each  other  and  how  the  joints  are  arranged  to  allow 
movement.  Observe  how  carefully  the  brain  and  the  spinal  cord  are 
protected,  and  also  the  thorax,  which  contains  the  heart  and  lungs. 
If  a  human  skeleton  is  procured,  notice  the  curving  of  the  spine 
which  enables  the  body  to  stand  erect. 

We  have  just  studied  briefly  some  of  the  invertebrates 
most  closely  related  to  the  welfare  or  injury  of  man.  Man 
himself  belongs  to  the  other  great  class, 
vertebrates.  The  higher  animals  which 
furnish  him  with  the  greater  part  of 
his  animal  food  also  belong  to  this 
class.  Although  there  are  great  vari- 
ations in  the  structure  of  vertebrate 
animals,  yet  they  are  alike  in  having 
a  backbone  and  an  inner  supporting 
skeleton. 

The  bony  skeleton  in  the  higher  forms 
of   animal   life   consists  of   a  vertebral 
column,    skull,    ribs    and    appendages. 
The   main   skeleton  protects  the  most 
delicate  organs  and  acts  as  a  support 
for  the  attachment  of  the  muscles.    The 
appendages,  like  the  legs  and  arms  in 
A  HUMAN  SKELETON,     man,  are    jointed   to   the    central   part 
of  the  skeleton,  and  it  is  the  action  of 
the  muscles  in  moving  these  about  the 
joints  that  makes  movement  from  place 
to  place  possible. 
In  the  skull  is  situated  the  great  nerve  center  of  the 
animal,  the  brain,  and  from   this  through  the  vertebral 


Notice  how  the  bones 
are  arranged  to  pro- 
tect the  delicate  or- 
gans. 


RESPIRATION 


225 


column  passes  the  great  nerve  distributor,  the  spinal  cord. 
From  the  spinal  cord, 
nerves  are  sent  to  all 
the  muscles  of  the  body, 
to  the  skin  and  to  those 
organs,  like  the  eye  and 
the  ear,  which  trans- 
mit to  the  brain  im- 
pressions received 
from  without  the  body. 
These  nerves  give  the 
stimulus  which  causes 
the  muscles  to  expand 
or  contract.  In  fact, 
all  the  voluntary  move- 
ments of  animals  are 
controlled  from  the 
brain  just  as  the  move- 
ments of  trains  on  a  rail- 
road are  controlled  from 
the  despatcher's  office. 

106.  Respiration.  — 
All  animals  must  have 
a  way  to  breathe,  or 
energy  cannot  be  sup- 
plied to  carry  on  the 
activities  of  the  body. 
Different  animals 
breathe  in  .  different 

ways,  but  in  the  higher  THE  NERVOUS  SYSTEM  OF  MAN. 

vertebrates  and  in  man      Notice  how  the  nerves  are  distributed  to 

it  is  the  same.     Respira-  a11  Parts  of  the  body • 

tion   in   man    will,   therefore,    be   taken    as   the   type. 
Air  enters  the  body  through  the  nose  or  mouth,  and 


226 


FIRST   YEAR   SCIENCE 


passes  down  through  the  windpipe  into  the  lungs.  In  order 
to  keep  out  dust  and  germs,  the  opening  of  the  nose  is 
supplied  with  a  large  number  of  hairs  projecting  from  the 
mucous  membrane  which  lines  the  whole  nasal  chamber. 
These  hairs  and  the  secretion  from  the  membrane  catch  and 

hold  most  of  the  harm- 

• 

ful  particles.  At  the 
back  of  the  mouth  the 
windpipe  and  the  throat 
come  together. 

When  food  is  being 
swallowed,  the  passage 
into  the  windpipe  must 
be  closed,  and  this  is 
done  by  the  little  valve- 
like  epiglottis.  If,  in 
swallowing,  the  epi- 
glottis is  not  able  to 
close  quickly  enough, 
something  may  pass  into  the  windpipe  and  cause  choking. 
The  windpipe,  at  the  upper  part  of  the  chest,  branches  into 
two  parts,  one  branch  going  to  each  of  the  lungs. 

The  lungs  fill  the  upper  part  of  the  chest  and  enfold 
the  heart.  In  them  the  air  tubes  divide  again  and  again, 
forming  a  vast  network  of  tubes  which  grow  smaller  and 
smaller  until  they  end  in  little  air  sacks.  Interlacing  with 
these  air  tubes  are  veins  and  arteries  which  carry  the  blood. 
The  tiniest  parts  into  which  the  blood  vessels  are  divided, 
the  capillaries,  form  close  networks  within  the  linings  of 
their  sacks.  The  air  and  blood  are  thus  separated  by  an 
exceedingly  thin  animal  tissue,  which  allows  an  exchange 
of  soluble  materials.  Thus  the  blood  is  able  to  take  up  the 
oxygen  needed  and  to  rid  itself  of  the  carbon  dioxide  and 
other  waste  products  which  it  has  accumulated. 


THE  LUNGS. 

They  are  here  pulled  aside  to  show  the 
heart. 


CIRCULATION  227 

The  air-tight  thoracic  cavity  in  which  the  heart  and 
lungs  are  situated  is  inclosed  and  protected  by  the  ribs 
and  at  the  lower  part  by  a  dome-shaped  muscle  called  the 
diaphragm.  Air  enters  the  lungs  because  the  muscles  of 
the  chest  pull  the  ribs  so  that  they  move  upward  and  out- 
ward and  the  muscles  of  the  dome-shaped  diaphragm  cause 
it  to  move  downward.  These  two  actions  enlarge  the 
thoracic  cavity.  The  air  enters  in  the  same  way  that  it 
enters  a  hollow  rubber  ball  that  has  been  compressed  and 
then  set  free.  When  the  ribs  move  downward  and  the 
diaphragm  upward,  the  air  is  expelled  as  in  the  rubber  ball 
when  compressed. 

There  are  then  two  ways  in  which  air  can  be  made  to 
enter  the  lungs,  the  "  raising  of  the  chest "  and  the  move- 
ment of  the  diaphragm.  In  the  proper  kind  of  breathing 
these  two  movements  go  on  together.  The  lungs  are  filled 
throughout  and  not  simply  at  either  the  top  or  bottom. 
If  this  is  to  be  accomplished,  the  body  must  be  free 
and  not  restricted  by  tight  clothing  about  the  chest  or 
the  lower  part  of  the  trunk  of  the  body,  the  abdomen. 
Not  only  is  the  right  kind  of  breathing  necessary  for 
properly  supplying  the  blood  with  oxygen,  but  also  that 
the  lung  tissues  themselves  may  be  properly  nourished 
and  cared  for.  We  should  be  particularly  careful  about 
this  now  that  infectious  diseases  of  the  lungs  are  so 
prevalent. 

107.  Circulation.  —  Experiment  116.  —  If  a  compound  microscope 
can  be  procured,  tie  a  string  tightly  around  the  end  of  a  clean  finger, 
and  when  it  has  become  full  of  blood,  prick  it  quickly  with  a  sterilized 
needle.  Rub  the  drop  of  blood  that  comes  out  on  a  glass  slide  and 
quickly  examine  under  the  microscope.  Notice  the  great  number  of 
round  disk-like  bodies,  red  corpuscles.  Try  to  find  an  irregular-shaped 
body  which,  while  the  blood  remains  fresh,  slowly  changes  its  shape, 
a  white  corpuscle.  These  are  rather  difficult  to  find,  but  can  be  seen 
if  the  drop  of  blood  is  thoroughly  examined  quickly  enough. 


228  FIRST    YEAR   SCIENCE 

In  order  that  all  parts  of  the  body  may  be  provided 
with  the  materials  used  in  building  their  cells  and  in  doing 
the  work  necessary  for  continued  existence  there  must  be 
a  distributory  system.  This  is  necessary  wherever  diver- 
sified work  is  to  be  carried  on.  This  necessity  has  brought 
into  effect  the  railway  and  canal  systems  of  the  world. 
The  body  is  a  little  world  by  itself,  and  it  has  a  most  com- 
plete and  wonderfully  adapted  system  for  supplying  the 
material*  needed  and  for  removing  the  waste.  The  center 
and  motive  power  of  this  system  is  the  heart.  The  medium 
of  circulation  is  the  blood. 

When  toe  blood  is  examined,  it  is  found  to  consist  of  a 
watery  liquid,  called  the  plasma,  a  great  number  of  little 

disk -shaped  bodies,  the  red  cor- 
puscles, and  some  irregular 
whitish  bodies,  the  white  cor- 
puscles (Fig.  108). 


°  ° 


°oo    °  corpuscles  are  protoplasmic  cells 

S  <?o  JLo  Oo   00§       having    various    functions    and 

OWO^O 

°o    oco°o   o   00°  °        possessing  the  power  of  move- 

o°      %  °oo  ment  and  even  of  working  their 

o 

way  out  of  the  blood  vessels. 

The  main  function  of  the  red 

corpuscles.is  to  carry  oxygen  from  the  lungs  to  the  different 
living  cells  of  the  body.  They  contain  a  pigment,  hcemo- 
globin,  which  carries  the  oxygen  and  gives  the  blood  its 
color.  The  plasma,  an  exceedingly  complex  fluid,  is  com- 
posed largely  of  water,  but  contains  the  nutrient  and  waste 
materials  supplied  by  the  different  organs  of  the  body. 

The  blood  passes  through  different  kinds  of  vessels. 
Those  leading  from  the  heart  are  called  arteries,  and  those 
returning  to  the  heart  are  called  veins.  As  the  arteries 
proceed  out  from  the  heart  they  divide  continually,  becom- 
ing smaller  and  smaller  until  they  terminate  in  very  small 


CIRCULATION 


229 


thin- walled  vessels  called  capillaries.  These  capillaries 
unite  and  form  veins.  Thus  the  blood  is  continually  flow- 
ing from  the  heart 
through  the  capillaries 
into  the  veins  and  back 
to  the  heart. 

As  a  rule  the  arteries 
are  below  the  surface  of 
the  body,  where  they 
are  protected,  but  if  the 
finger  is  placed  on  the 
wrist  or  the  side  of-  the 
face  near  the  ear,  an 
artery  can  be  felt 
through  which  the  blood 
is  pulsing.  The  veins 
can  be  seen  in  the  back 
of  the  hand  and  a  pin 
piercing  the  body  any- 
where will  break  open 
some  of  the  capillaries 
and  cause  blood  to  ooze 
out.  The  capillaries 
spread  throughout  the 
entire  tissue  of  the  body 
and  supply  with  food 
and  oxygen  the  different  living  cells  of  which  the  body  is 
composed. 

The  heart  is  a  muscular  force  pump  composed  of  four 
chambers,  two  auricles  and  two  ventricles.  It  is  shaped 
somewhat  like  a  pear  and  is  situated  almost  directly  be- 
hind the  breastbone.  The  blood  coming  back  from  the 
veins  flows  into  the  right  auricle,  a  chamber  with  rather 
flabby  walls.  From  here,  it  passes  through  a  valve  into 


THE  CIRCULATORY  SYSTEM. 
Notice  that  the  veins  (white)  are  out- 
side of  the  arteries  (black). 


230  FIRST   YEAR   SCIENCE 

'  V  .  ,,* 

the  right  ventricle,  which  is  a  chamber  with  very  thick 
muscular  walls.  From  the  right  ventricle,  the  blood  is 
driven  out  through  the  arteries,  capillaries  and  veins  of 
the  lungs,  where  carbon  dioxide  is  given 
off  and  oxygen  absorbed  by  the  red  cor- 
puscles. 

Returning  from  the  lungs,  the  blood 
enters  the  left  auricle  and  when  this  be- 
comes full,  passes  through  a  valve  into 
the  left  ventricle.  This  has  such  power- 
fully muscular  walls  that  it  is  able  to 

force  the  blood  throughout  the  body  and 
CROSS  SECTION  OF  / 

THE  HUMAN  HEART,   back  again  to  the  right  auricle.     As  the 

Showing  auricle,      blood  leaves  either  ventricle,  there  are 

ventricle  and  ven-      vaives  that  close  and  prevent  its  return. 

If  the  hand  is  placed  a  little  to  the  left 

of  the  breastbone,  the  strong  contraction  of  the  ventricle 

can  be  felt. 

108.  The  Senses.  —  In  order  that  the  brain  may  com- 
municate with  the  outside  world  and  so  be  able  to  protect 
the  animal  from  destruction  and  to  provide  for  its  well- 
being,  animals  have  become  provided  with  a  number  of 
sense  organs  which  communicate  with  the  brain  by  the 
nerves.  The  most  conspicuous  sensations  of  the  human 
body  are  sight,  hearing,  taste,  smell  and  touch. 

The  organ  of  sight,  the  eye,  is  an  exceedingly  sensitive, 
automatically  adjustable  camera  that  records  through  the 
nerves.  The  camera  box  is  the  hard  bony  socket  in  which 
it  is  placed,  the  eyelid  is  the  shutter,  and  the  iris,  the  dia- 
phragm. The  iris  is  the  membrane  in  the  front  of  the  eye 
which  opens  or  contracts  to  let  in  more  or  less  light.  In 
the  center  of  it  is  a  hole,  the  pupil. 

Back  of  the  shutter,  or  iris,  is  a  small  adjustable  lens 
and  beyond  this  the  sensitive  plate,  the  retina.  Between 


THE  SENSES 


231 


RETINA 


the  iris  and  the  front  of  the  eye  is  a  watery-like  material, 
the  aqueous  humor,  which  keeps  the  front  of  the  eye  ex- 
tended into  its  rounded 
form.     Back  of  the  lens 
is    a    thick,  transparent, 
jelly-like    material,     the 
vitreous     humor,      which 
holds  the  retina  extended 
and  keeps  the  eye  from 
collapsing. 

Instead  of  moving  the 
retina  back  and  forth  to 

CROSS  SECTION  OF  THE  HUMAN  EYE. 


The  pupil  is  the  opening  between  the 

upper  and  lower  parts  of  the  iris  as 

shown  in  the  figure. 


focus  a  picture,  as  is  done 

with     the     ground-glass 

plate    in    a   camera,   the 

eye    lens    is    capable    of 

adjusting  itself  so  as  to  focus  objects  which  are  at  different 

distances.     Leading  back  to  the  brain  from  the  retina,  is 

the  optic  nerve,  which  carries  the  impressions  made  on  the 

retina  to  the  brain  where 
they  are  interpreted  into 
the  sensation  of  sight. 

This  rough  comparison 
is  by  no  means  a  descrip- 
tion of  the  eye,  for  it  is  a 
most  complex  and  wonder- 
ful organ,  vastly  superior 
in  construction  to  a 
camera.  A  technical  de- 
scription would,  however, 

be  out  of  place  here. 
CROSS  SECTION  OF  THE  HUMAN  EAR.  mi  i  •  i      •      ,r 

Ine  ear,  wnicn  is  the 

sound  transmitter,  consists  of  the  outer  ear,  which  is  so 
arranged  as  to  catch  the  sound  waves  and  converge  them 


232  FIRST   YEAR   SCIENCE 

'  '  '  •  /* 

upon  the  ear  drum.  The  ear  drum  is  a  thin  membrane 
stretched  tightly  across  a  bony  opening  and  vibrating  when 
the  air  waves  strike  it,  as  a  drum  does  when  struck  by  the 
drumstick.  On  its  inner  side  the  drum  is  attached  to  the 
inner  ear  by  a  chain  of  three  bones.  The  sensitive  cells 
of  the  inner  ear  transmit  the  impressions  made  by  the 
sound  vibrations  through  the  auditory  nerve  to  the  brain, 
where  they  are  interpreted  into  the  sensation  of  sound. 

On  the  tongue  and  in  the  nose  are  cells  which  transmit  to 
the  brain  the  impressions  produced  upon  them  by  different 
qualities,  the  one  of  solutions  and  the  other  of  gases.  The 
sensations  thus  produced  are  called  taste  and  smell. 

The  sensation  of  touch  originates  in  the  skin  and  is  much 
more  acute  in  some  portions  than  in  others.  The  tips  of 
the  fingers  in  the  blind  are  often  trained  to  such  delicate 
perception  that  they,  in  a  great  degree,  take  the  place  of 
the  lacking  sense  organ.  These  sensations,  like  all  others, 
are  carried  to  the  brain  by  the  nerves  and  there  inter- 
preted into  the  sensation  of  touch. 

109.  Food. — Experiment  117.  —  Chop  a  piece  of  the  white  of  a 
hard-boiled  egg  into  pieces  about  as  large  as  the  head  of  a  pin  and 
place  in  a  test  tube.  Chop  up  another  piece  much  finer  than  this  and 
place  it  in  a  second  test  tube.  Make  a  mixture  of  100  cc.  of  water,  5  cc. 
of  essence  of  pepsin  and  2  cc.  of  hydrochloric  acid.  Pour  into  each 
test  tube  enough  of  this  mixture  to  cover  the  white  of  egg  to  a  con- 
siderable depth.  Shake  thoroughly  and  put  in  a  place  where  the  tem- 
perature can  be  maintained  at  37°  C.  or  98°  F.  A  fireless  cooker  or  a 
bucket  of  warm  water  is  good  for  this.  Allow  to  stand  for  several 
hours,  keeping  the  temperature  constant.  The  white  of  egg  is  dis- 
solved, the  action  being  more  rapid  in  the  second  tube.  Try  the  same 
experiment  using  water;  using  dilute  hydrochloric  acid.  Do  these 
have  the  same  effect  as  when  used  with  the  pepsin?  The  pepsin 
solution  is  an  artificial  gastric  juice. 

In  order  that  the  work  of  the  body  may  be  carried  on, 
food  is  required.  This  food  may  be  supplied  by  either 


DIGESTION 


233 


Salivary 
Olands  ^H 


animals  or  plants.  The  original  source  of  all  animal  and 
plant  food,  as  has  been  seen,  is  in  the  chlorophyll  manu- 
factory of  the  leaf  and  green  stem.  After  this  leaf  food 
has  been  manufactured,  it  is  simply  modified  by  the  plants 
and  animals  through  which  it  passes.  The  food  is  used 
(1)  in  growing  new  cells,  (2)  in  repairing  cells  that  have 
been  used  up  or  destroyed,  (3)  in  providing  energy  to 
carry  on  the  activities  of  the  body  and  maintain  its  heat 
or  (4)  in  doing  external 
work,  such  as  moving  the 
body  itself  from  place  to 
place  or  moving  other 
bodies. 

To  furnish  any  of  this 
energy,  the  cells  must  be 
able  to  combine  food  with 
oxygen.  To  do  this  the 
food  must  be  digested  or 
prepared  so  that  it  can 
pass  through  animal  tis- 
sue. In  the  higher  ani- 
mals,  a  complicated  ap- 
paratus  is  provided  to 
accomplish  this.  In  man, 
it  is  briefly  as  follows  : 
a  long  continuous  tube,  the 
food-tract  or  the  alimen- 
tary canal  (Fig.  109),  ex- 
tends through  the  body. 
Different  portions  of  this  tube  are  adapted  to  different 
processes.  In  the  mouth,  the-  teeth  grind  the  food  into 
small  bits  and  mix  it  with  the  saliva.  This  is  an  exceed- 
ingly important  part  of  the  process,  because  if  the  food  is 
•not  ground  fine,  the  digestive  juices  cannot  readily  get  at 


Fig.   109. 


234  FIRST   YEAR   SCIENCE 

it,  and  the  whole  process  of  digestion  is  greatly  retarded. 
Thus  much  more  energy  is  expended  than  otherwise  would 
be.  The  saliva  is  necessary  to  digest  some  of  the  starch 
and  to  aid  in  the  further  digestion. 

The  food  passes  from  the  mouth  down  the  throat  and 
through  a  valve  into  the  stomach.  This  is  a  large  pouch 
which  will  hold  Usually  from  three  to  four  quarts.  It  has 
muscular  walls  which  enable  it  to  contract  and  expand, 
thus  keeping  the  food  moving  about  so  that  it  is  thoroughly 
mixed  with  the  gastric  juice.  The  gastric  juice  is  secreted 
by  little  glands  thickly  imbedded  in  the  lining  of  the 
stomach.  Artificial  gastric  juice  was  made  in  Experi- 
ment 117.  Some  of  the  proteins  (Experiment  119)  are 
digested  in  the  stomach,  although  the  larger  part  of 
digestion  takes  place  in  the  small  intestine. 

From  the  stomach  the  food  passes  through  a  valve  into 
the  small  intestine.  This  is  a  complexly  coiled  tube  which 
fills  the  larger  part  of  the  abdomen.  The  inner  wall  of 
the  tube  is  lined  with  glands  which  secrete  digestive  juices, 
and  into  the  intestine  are  poured  the  secretions  from  two 
large  glands,  the  pancreas  and  the  liver.  The  small 
intestine  is  the  great  digestive  organ  of  the  body.  Here 
the  fats  and  oils  (Experiment  120)  are  digested  and  the 
digestion  of  the  starches  and  proteins  is  completed.  The 
small  intestine  opens  through  a  valve  into  the  large  in- 
testine, a  tube  five  or  six  feet  long  decreasing  in  size 
toward  the-  exit  to  the  body.  There  is  little  digestion  in 
the  large  intestine. 

The  changes  that  take  place  in  the  food  as  it  passes 
through  the  alimentary  canal  are  very  complex,  but  dur- 
ing its  progress  the  valuable  part  of  the  food  is  so  changed 
and  prepared  that  it  can  be  absorbed  by  the  blood  and 
transported  by  it  to  the  different  parts  of  the  body  where 
its  energy  is  needed.  Absorption  takes  place  all  along 


NECESSARY  FOODS  235 

the  alimentary  canal  wherever  the  food  has  been  suffi- 
ciently prepared. 

110.  Necessary  Foods.  —  Experiment  118.  —  Place  in  different 
test  tubes  small  amounts  of  (1)  corn  starch,  (2)  grape  sugar, 

(3)  scrapings  from  a  raw  potato,  (4)  flour,  and  (5)  the  white  of  an 
egg.    Pour  in  a  little  water  and  shake  thoroughly.     Drop  into  each 
tube  a  few  drops  of  the  iodine  solution  prepared  in  Experiment  100. 

Experiment  119.  —  Place  in  test  tubes  small  quantities  of  (1)  the 
white  of  a  hard-boiled  egg,  (2)  tallow  or  lard,  (3)  grape  sugar,  and 

(4)  any  other  food  which  may  be  handy.     Pour  a  little  concentrated 
nitric  acid  into  each  tube  and  allow  to  stand  for  a  minute.     Be  care- 
ful not  to  get  the  nitric  acid  on  the  clothes  or  hands.     Pour  the  acid 
out  into  a  slop  jar  and  wash  the  substances  with  a  little  water.    Pour 
off  the  wash  water  and  pour  on  a  little  strong  ammonia.     If  the  sub- 
stances turn  a  yellow  or  orange  color,  proteins  are  present.     Which 
substances  contain  proteins  ? 

Experiment  120.  —  Gasoline  vapor  is  very  inflammable,  so  be  sure 
in  this  experiment  that  there  is  no  flame  in  the  room.  Place  about  a 
spoonful  of  (1)  both  the  white  and  the  yellow  of  an  egg,  (2)  flaxseed 
meal,  (3)  yellow  corn  meal,  (4)  white  flour,  and  (5)  other  foods  it  is 
desired  to  test  in  separate  evaporating  dishes  or  beakers  near  an  open 
window.  Pour  on  to  these  enough  gasoline  to  more  than  cover  them 
and  stir  thoroughly.  Cover  the  evaporating  dishes  and  allow  to  stand 
for  ten  or  fifteen  minutes.  Pour  the  gasoline  off  into  a  beaker  and 
set  the  beaker  outside  the  window  until  the  gasoline  has  evaporated. 
If  there  is  anything  left  it  must  have  been  dissolved  from  the  food. 
If  a  substance  remains,  place  a  drop  of  it  on  a  piece  of  paper.  Smell 
of  it.  Try  to  mix  it  with  water.  Rub  it  between  the  fingers.  Try 
any  other  fat  or  oil  test  of  which  you  can  think. 

Experiment  121.  —  In  a  place  where  there  is  a  good  draft  so  that 
odors  will  not  penetrate  the  room,  burn  in  an  iron  spoon  over  a  Bun- 
sen  burner  (1)  small  pieces  of  meat,  (2)  a  little  condensed  milk  or 
milk  powder,  (3)  part  of  an  egg,  and  (4)  any  other  food.  Is  there  a 
residue  left  after  burning  ?  If  so,  this  is  mineral  matter. 

In  Experiments  118-121  we  found  that  our  ordinary 
foods  are  of  three  great  groups  of  chemical  compounds, 
carbohydrates  (starches  and  sugars),  proteins,  and  fats  or 


236 


FIRST  YEAR   SCIENCE 


oils.  The  common  foods  that  consist  largely  of  proteins 
are  lean  meat,  cheese,  eggs,  beans,  and  peas.  Those 
largely  composed  of  carbohydrates  are  most  cereals,  vege- 
tables and  fruits.  The  fats  are  butter,  pork,  nuts  and 
chocolate.  Milk  contains  all  three  of  these  compounds 
in  approximately  the  proportion  needed  by  the  body. 

Careful  experiment 
has  shown  that  the  aver- 
age, full-grown  American 
needs  each  day  two  to 
three  ounces  of  proteins, 
about  four  ounces  of  fats 
and  a  pound  of  carbo- 
hydrates. The  weight 
of  food  eaten,  however, 
is  very  much  greater  than 
this,  as  all  foods  are  com- 
posed largely  of  water. 
The  proteins  are  needed 
for  growth  and  repair, 
since  the  living  part  of 
the  cells,  the  protoplasm, 
is  composed  of  proteins. 
The  rest  of  the  food  furnishes  energy. 

Until  recently,  it  was  thought  that  a  great  deal  of  meat 
was  necessary  to  furnish  the  energy  needed  for  hard  mus- 
cular work.  But  now  investigation  has  shown  that  this 
energy  can  better  be  supplied  by  other  foods  and  that  eat- 
ing too  much  meat  is  not  only  needlessly  expensive  but 
bad  for  the  system.  The  staple  food  of  northern  Africa 
and  southwestern  Asia  is  the  date  palm,  which  is  admi- 
rable for  hot  climates.  In  cold  regions  where  the  body 
requires  great  energy  to  keep  up  its  heat,  much  fat  is 
eaten  and  sugar,  if  procurable.  The  exact  khid  of  food 


A  DATE  PALM. 


NECESSARY  FOODS 


237 


used  must  always  depend  largely  on  its  availability  and  on 
the  tastes  of  the  individual,  but  the  diet  should  be  so  varied 
as  to  contain  sufficient  of  each  of  the  three  great  classes 
of  foods. 

Besides  the  necessary   foods,  most   individuals   desire 
especial  additions  for  relishes  and  beverages.     These  com- 
monly consist  of  spices,  tea  and 
coffee  and  other  like  materials. 
When  used  in  moderation,  they 
are    usually    a    benefit,   as    they 
stimulate  the  appetite.     But  ex- 
cessive use  is  harmful. 

Alcohol,  except  possibly  in  ex- 
ceedingly small  quantities,  can- 
not be  considered  a  food,  and  as 
a  stimulator  for  the  appetite  it 
should  not  be  used.  Many  care- 
ful experiments  have  shown  that 
while  it  may  stimulate  the  body 
temporarily,  it  does  not  enable  it 
to  do  more  work.  Instead,  those  using  it  cannot  do  as 
much  work,  or  withstand  as  great  physical  or  mental 
strain,  as  those  not  using  it.  Even  if  it  were  not  for  the 
ungovernable  appetite  which  its  use  almost  invariably  en- 
genders, and  for  the  degrading  influences  with  which  its 
use  is  usually  surrounded,  its  physiological  action  is  such 
as  to  lessen  the  body's  vitality,  decrease  its  resistance  to 
disease,  and  dull  its  nervous  and  mental  efficiency. 

Careful  scientific  experiments  have  also  been  made  upon 
the  effect  of  tobacco.  Although  there  are  differences  of 
opinion  about  its  effect  upon  fully  matured  adults,  there 
is  no  such  difference  of  opinion  in  regard  to  its  effect  upon 
those  who  have  not  stopped  growing  and  are  not  yet  fully 
matured.  Measurements  and  comparisons  made  in  regard 


A  BUNCH  OF  DATES. 


238 


FIRST   YEAR   SCIENCE 


to  the  physical  development,  endurance  and  mental 
ability  of  a  large  number  of  college  men  has  shown  con- 
clusively that  those  who  have  not  used  ttfbacco,  as  a  rule, 
have  better  physiques,  are  better  students  and  can  stand 
more  physical  exercise  than  those  who  have  used  it.  In  the 
competition  for  athletic  teams  it  is  found  that  only  about 
half  as  many  of  those  who  have  used  tobacco  make  good, 
as  of  those  who  have  not  used  it. 


COFFEE  PLANT. 
Showing  the  clusters  of  beans  from  which  coffee  is  produced. 

111.  Preparation  of  Foods.  —  When  foods  are  appetizing, 
look  good,  smell  good  and  taste  good,  both  the  saliva  and 
the  gastric  juice  are  secreted  in  larger  quantities,  so  that 
this  sort  of  food,  when  taken  into  the  system,  is  more  read- 
ily digested  than  food  which  is  not  attractive.  One  of  the 
reasons  for  cooking  food  is  to  render  it  appetizing,  and 
this  should  never  be  lost  sight  of  by  the  cook.  Cooking 
also  softens  and  loosens  the  fibers  of  meats  and  causes  the 


SUMMARY  239 

cell  walls  of  the  starch  granules  to  burst,  thus  rendering 
it  possible  for  the  digestive  juices  to  attack  the  food  more 
readily.  In  addition,  cooking  kills  the  germs  and  other 
parasites  that  are  sometimes  found  in  foods. 

To  cook  food  properly  is  a  fine  art  and  requires 
most  careful  study  and  great  skill.  The  science  of  pro- 
viding economically  the  kinds  of  food  necessary  and  of 
cooking  these  properly  so  that  they  will  be  attractive, 
easily  digested  and  will  lose  none  of  their  nutritive  value, 
is  one  that  is  at  present  in  its  infancy.  Human  beings, 
like  other  animals,  must  have  a  balanced  ration  or  diet  if 
they  are  to  be  most  productive  economically.  They  differ 
from  other  animals  in  having  a  much  greater  range  of  food 
possibilities  and  in  being  much  more  sensitive  as  to  the 
appearance  and  taste  of  food. 

Summary.  —  Plants  and  animals  form  the  live  part  of 
the  earth.  Most  plants  consist  of  root,  stem  and  leaves. 
The  root  takes  in  all  the  plant's  food  except  carbon  and 
oxygen.  These-  are  supplied  through  the  leaves.  The 
leaves  are  the  original  food  manufactories  for  all  plants 
and  animals.  They  are  supported  on  the  stem,  of  which 
there  are  two  great  classes,  monocotyledonous  and  dicotyle- 
donous. 

The  stems  also  support  the  flower,  which  usually  con- 
sists of  calyx,  corolla,  stamen  and  pistils.  The  chief 
function  of  the  flower  is  to  produce  the  seeds  by  which 
the  plants  are  reproduced.  The  pollen  grains  which  are 
necessary  for  the  fertilization  of  the  egg  cells  are  carried 
and  spread  by  the  wind  and  by  insects  and  birds.  The 
seeds  are  also  scattered  by  the  wind  and  by  animals  and 
sometimes  by  floating  down  streams. 

Besides  these  green  plants  there  is  another  class  called 
fungi.  Instead  of  preparing  their  own  food  by  the  help 


240  FIRST   YEAR   SCIENCE 

of  the  sun  and  the  soil,  they  live  upon  the  food  prepared 
by  the  green  plants. 

Probably  the  simplest  plants  are  the  baeteria,  single-cell 
plants,  which  multiply  very  rapidly.  Bacteria  and  fungi 
cause  many  diseases  as  well  as  most  of  the  spoiling  of 
food.  Disease  bacteria  are  usually  called  germs.  Their 
effects  may  be  counteracted  by  the  use  of  disinfectants 
and  antitoxins. 

Animals  take  their  energy  indirectly  from  the  foods 
prepared  by  green  plants  or  by  other  animals.  They  are 
usually  classed  as  invertebrate  and  vertebrate.  The  lowest 
form  of  invertebrate  is  the  protozoon.  Worms  and  in- 
sects are  other  forms  of  invertebrates,  the  importance  of 
which  is  seldom  realized. 

Vertebrates  usually  have  a  backbone,  skull,  ribs  and 
appendages.  In  the  skull  is  the  brain,  connected  to  the 
various  parts  of  the  body  by  nerves.  Vertebrates  breathe 
by  u  drawing  "  air  through  the  windpipe  into  the  lungs. 
This  is  done  by  the  muscles  of  the  chest  and  diaphragm. 
The  lungs  purify  the  blood,  which  circulates  from  the 
heart  through  the  arteries  and  capillaries  and  back  through 
the  veins. 

The  five  senses  are  sight,  hearing,  taste,  smell  and 
touch.  These  sensations  are  carried  to  the  brain  by  the 
nerves,  and  they  come  from  the  eye,  the  ear,  the  nose,  the 
mouth  and  the  skin,  respectively. 

For  all  the  activities  of  body  and  brain,  food  is  required. 
As  food  passes  through  the  alimentary  canal,  various 
juices  are  mixed  with  it  and  certain  parts  of  it  are 
digested  and  absorbed  into  the  body.  Foods  are  of  three 
kinds,  proteins,  carbohydrates  and  fats,  and  we  need  a 
certain  percentage  of  each  for  proper  nourishment. 
Usually  foods  are  most  nourishing  and  most  appetizing 
when  properly  cooked. 


SUMMARY  241 

QUESTIONS 

Why  should  plants  and  animals,  like  other  earth  phenomena,  be 
studied  in  this  course  ?  • 

What  are  the  three  parts  into  which  most  plants  can  be  readily 
separated?  In  what  three  respects  are  plants  and  animals  alike? 
What  do  the  plant  roots  do  for  the  plant?  How  do  they  do  it? 
Describe  some  different  kinds  of  stems  that  you  have  seen,  and  ex- 
plain their  adaptability  or  lack  of  adaptability  for  making  the  best  of 
the  conditions  where  they  were. 

What  do  the  leaves  do  for  the  plant?     How  do  they  do  it?     • 

What  is  the  value  to  the  plant  of  the  flower  ?  How  are  the  flowers 
prepared  to  carry  out  their  part  in  the  life  struggle  of  the  plant? 
Describe  any  way  in  which  you  know  that  animals  have  been  of 
assistance  to  plants. 

How  do  plants  provide  for  the  dispersal  of  their  seeds? 

How  does  the  seed  develop  into  a  plant? 

With  what  useful  or  what  harmful  fungi  have  you  ever  had  any 
experience  ? 

In  what  ways  are  bacteria  helpful  and  in  what  ways  harmful  to 
mankind?  How  are  harmful  bacteria  guarded  against? 

How  are  plants  and  animals  mutually  helpful  to  each  other? 

Name  and  describe  some  of  the  invertebrate  animals  you  know1. 

How  have  we  found  that  the  angleworm  benefits  the  soil? 

What  is  the  use  to  the  vertebrate  of  the  skeleton  and  the  nervous 
system  ? 

Describe  how  vertebrate  animals  breathe.  Why  is  it  vitally 
necessary  for  them  to  breathe  freely  ? 

What  is  the  use  of  the  blood?  How  does  it  get  around  to  where  it 
is  needed  ? 

Describe  the  ways  in  which  man  becomes  aware  of  what  is  outside 
his  body. 

Why  is  food  needed  ?     How  and  where  is  it  digested  ? 

What  are  the  three  great  groups  into  which  foods  are  divided? 
Why  should  you  not  use  alcohol  or  tobacco  ? 

Why  is  cookery  one  of  the  most  useful  arts? 


CHAPTER   Vl'l 


LIFE  OF  THE  EAKTH  AS  EELATED  TO  PHYSICAL 
CONDITIONS 

112.  Ancient  Life  History.  —  As  the  rock  layers  of  the 
earth  are  explored,  fossils  of  different  kinds  of  plants 
and  animals  are  discovered.  The  fossils  of  the  more 
recent  rock  layers  correspond  very  closely  to  the  plants 
and  animals  that  are  found  upon  the  earth  to-day,  but 
the  older  the  layers,  the  less  they  correspond.  There 
seems  to  have  been  a  gradual  development  in  life  forms 
through  the  past  ages,  a  fragmentary  record  of  which 

is  engraved  upon  cer- 
tain of  the  sedimentary 
rocks.  Rocks  which 
were  formed  under  dif- 
erent  conditions  contain 
different  species  of  life 
forms,  showing  that 
throughout  all  time  the 
geographic  condition  has 
had  a  marked  influence 
upon  plants  and  animals. 
The  rocks  and  fossils 
show  that  the  geographical  conditions  of  certain  areas  also 
have  varied  greatly.  Some  regions  have  been  below  and 
above  the  sea  several  times.  Regions  now  cold  have  been 
warm,  and  those  now  dry  have  been  wet,  and  vice  versa. 
Thus  the  life  in  certain  areas  has  suffered  great  changes 
by  the  geographical  accidents  to  which  the  region  has 
been  subjected.  The  petrified  forests  near  Holbrook, 

242 


PETRIFIED  TREES. 
Found  near  Holbrook,  Arizona. 


DISTRIBUTION  OF  LIFE 


243 


Arizona,  show  some  of  the  most  remarkable  tree  fossils 
ever  found  and  indicate  that  the  region  has  been  sub- 
jected to  remarkable  geographical  changes. 

113.  Distribution  of  Life.  —  Plants  and  animals  are  found 
wherever  the  conditions  are  suitable  for  their  existence. 
In  ice-covered  areas,  like  the  interior  of  Greenland,  and 
in  exceedingly  dry  regions,  like  the  Sahara  and  certain 
parts  of  southwestern  United  States,  there  is  little  life  of 

any  kind.     With  a  few    : 

such  exceptions,  how- 
ever, the  surface  of  the 
earth  is  a  universal  bat- 
tlefield of  plants  and 
animals  struggling  to 
exist  and  to  increase. 
They  extend  themselves 
wherever  attainable 
space  is  opened.  But 
barriers  may  oppose  their 
spread  and  geographical 
accidents  may  drive  them 
from  areas  which  they 


GILA  MONSTERS. 

The  most  poisonous  reptiles  of  the  south- 
western American  desert. 


had  heretofore  held. 
The  retreat  of  the  sea 
may  cause  a  change  in 
the  position  of  shore  life.  In  the  water  a  land  barrier 
or  an  expanse  of  deep  water  may  prevent  the  spread  of 
shore  forms.  On  the  land  a  mountain  uplift,  a  desert 
area,  or  a  water  barrier  may  limit  the  space  occupied  by 
animal  and  vegetable  species. 

Certain  plants  and  animals  are  much  more  widely  dis- 
tributed than  others.  Plants  like  the  dandelion  and 
thistle,  whose  seeds  are  easily  blown  about  by  the  wind, 
spread  rapidly,  while  trees  like  the  oak  and  chestnut 


244 


FIRST   YEAR   SCIENCE 


spread  slowly.  As  plants  have  not  the  power  to  move 
about,  they  cannot  distribute  themselves  as  easily  as  ani- 
mals. '  Certain  birds 
which  are  strong  of 
flight  are  found  widely 
distributed  over  regions 
separated  by  barriers 
impassable  to  other  ani- 
mals. 

Some  of  the   present 

^jflPffffli  'J*ffr.  barriers  to  life  distribu- 
tion have  come  into  ex- 
istence in  comparatively 
recent  geological  time. 
There  is  good  reason  to 
believe  that  the  British 
Isles  and  Europe  were 
formerly  connected,  and 
that  in  very  ancient 
times  Australia  was 
joined  to  Asia.  It  is  also 
believed  that  for  long 
ages  North  and  South 
America  were  separated 
by  a  water  barrier  and  that  even  after  they  were  once 
connected,  the  Isthmus  of  Panama  was  again  submerged. 
These  are  but  a  few  illustrations  of  the  changes  in  the 
earth's  surface  which  have  affected  the  distribution  of 
animals  and  plants.  Climatic  changes  like  that  which 
brought  about  the  great  ice  advance  of  the  Glacial  Period 
have  affected  in  a  marked  degree  the  distribution  of  life. 
It  is  thus  found  that  when  a  study  is  made  of  the  present 
distribution  of  life,  careful  attention  must  be  given  to  the 
present  and  past  geographical  conditions  of  the  region. 


CANADA  THISTLE. 

One  of  the  most   widely  distributed  of 
plants. 


ADAPTABILITY  OF  LIFE 


245 


114.   Adaptability     of    Life.— 

There  is  hardly  a  place  on  the 
earth's  surface  not  adapted  to 
some  form  of  life.  Even  upon 


CACTI. 

These  are  adapted  to  desert 

life  because  they  have  no 

leaves   from   which   water 

can  evaporate. 


A  RATTLESNAKE  COILED  READY  TO 

SPRING. 

The  color  of  these  reptiles  makes  them 
hardly  distinguishable  from  the  sur- 
rounding desert. 

the  ice-bound  interior  of  Greenland  a  microscopical  plant 
and  a  tiny  worm    have  found  a  home.     The  dry   desert 

regions  have  a  few 
plants  with  small  leaves 
or,  like  the  cactus,  with 
no  true  leaves.  This 
prevents  the  evapora- 
tion of  the  water  from 
their  surfaces  and  so 
protects  them  from 
drought.  To  protect 
them  from  animals, 
many  of  these  plants 
are  armed  with  thorns. 
Another  example  of 
adaptability  is  the  fact 
that  the  small  animals 
of  the  desert  are  gen- 


A  HERD  OF  REINDEER. 

This  animal  is  of  invaluable   service  to 

man  in  polar  regions. 


246 


FIRST   YEAR   SCIENCE 


erally  of  a  sandy  color,  which  makes  them  hardly  dis- 
tinguishable from  their  desert  surroundings.  The  large 
ones  are  swift  strong  runners,  like  the  antelope  and 

ostrich,  or,  like  the 
camel,  are  able  to  travel 
for  long  distances  with- 
out water. 

In  the  colder  regions 
the  plants  have  the 
power  of  rapid  growth 
and  germination  during 
the  short  season  when 
the  snow  has  melted 
away.  Then,  during 
the  long  winter,  they 
lie  dormant  but  un- 
harmed under  the  snow 
and  ice.  The  animals 
are  either  able,  like  the 
reindeer,  to  live  upon 
the  dry  mosses,  lichen 
and  stunted  bushes,  or 
else  upon  other  ani- 
mals. Their  color,  like 
that  of  the  polar  bear, 
often  blends  with  their 
surroundings. 

Some  animals  have  a 
wide  range  of  adapta- 
bility, like  the  tiger, 
which  is  found  from 
the  equator  to  Siberia. 
But  usually  the  range 
of  an  animal  species  is 


TIGER. 

One  of    the  most  widely  distributed  of 
animals. 


ADAPTABILITY  OF  LIFE 


247 


much  more  restricted,  since  it  is  seldom  able  to  adapt 
itself  to  widely  differing  conditions.  The  surrounding 
region,  the  elevation,  the  temperature,  the  amount  of 
moisture,  the  soil,  the  kinds  of  winds  and  their  force,  all 
have  a  marked  effect  upon  the  fauna  (animals)  and  flora 
(plants)  of  a  country. 

The  species  that  thrive  in  a  region  must  have  adapted 
themselves  to  the  existing  conditions,  yet  other  animals 
and  plants  may  be  as  well  adapted  for  certain  regions  as 


A  CALIFORNIA  RABBIT  DRIVE. 

In  some  communities  rabbits  become  such  a  pest  that  the  inhabitants  turn 
out  in  a  body  and  drive  them  into  enclosures. 

thqse  now  inhabiting  them.  Striking  examples  of  this 
are  the  English  sparrow  and  the  gipsy  moth,  which  have 
spread  with  such  tremendous  rapidity  since  their  introduc- 
tion into  this  country.  The  rabbit  in  Australia  and 
southern  California  is  another  striking  example.  The 
adaptability  of  plants  to  a  new  region  is  also  illustrated  by 


248 


FIRST   YEAR   SCIENCE 


the  Russian  thistle  which  was  introduced  into  this  country 
in  1873  and  which  has  now  become  a  national  pest. 

115.  Life  of  the  Sea.  —  The  plants  living  in  the  sea  are 
nearly  all  of  a  low  order.  The  mangrove  trees  which 
border  some  tropical  shores  represent  their  highest  type. 
The  most  abundant  of  sea  plants,  the  seaweeds,  have  no 


DIFFERENT  KINDS  OF  SEAWEED. 

flower  or  seed  or  true  root,  although  most  of  them  have 
an  anchoring  device  by  which  they  are  attached  to  the 
bottom.  Their  food  is  absorbed  from  the  surrounding 
water.  They  have  developed  little  supporting  tissue,  fcut 
instead  have  bladder-like  air  cavities  or  floats,  which 
enable  them  to  maintain  an  erect  position  or  to  float  freely 
in  the  water.  Usually  they  abound  near  the  shore  where 
the  water  is  shallow.  4 

The  vast  surface  of  the  open  sea  supports  few  plants 


LIFE  OF  THE  SEA 


249 


except  the  minute  one-celled  plants,  the  diatoms,  of  which 
there  are  many  species  and  an  almost  infinite  number  of 
individuals.  These  furnish  about  the  only  food  for  the 
animals  of  the  open  sea  except  that  obtained  by  preying 
upon  each  other. 

A  great  quantity  of  detached  seaweed  (Sargassum), 
filled  with  multitudes  of  small  marine  animals  and  the 
fishes  which  prey  upon  them,  covers  the  surface  of  the 
middle  Atlantic,  the  center  of  the  oceanic  eddy.  Through 
this  Columbus  sailed  from  the  16th  of  September  to  the 
8th  of  October,  1492,  greatly  to  his  own  astonishment 
and  to  the  terror  of  his  crew,  who  had  never  before  heard 
of  these  "oceanic  meadows." 

The  animals  of  the  sea  vary  in  size  from  the  microscopic 
globigerina,  whose  tiny  shells  blanket  the  beds  of  the 

deeper    seas,    to    the        _. 

whale,  that  huge  giant 
of  the  deep,  in  compari- 
son with  which  the 
largest  land  animals  are 
but  pigmies.  Although 
monarch  of  all  the  finny 
tribe,  it  is  not  a  fish  at 
all,  but  a  mammal  which 
became  infatuated  with 
a  salt-water  life  and  so 
through  countless  ages  has  more  and  more  assumed  the 
finny  aspect.  It  is  obliged  to  rise  to  the  surface  to 
breathe.  It  cares  for  its  young  like  other  mammals. 

Here,  too,  are  found  the  jellyfish,  the  Portuguese  man- 
of-war  (Fig.  110),  some  fishes,  many  crustaceans,  a  few  in- 
sects, turtles,  snakes  and  mammals.  Most  of  these  animals 
are  lightly  built  and  are  well  equipped  for  floating  and 
swimming.  Some  sea  animals,  like  the  oyster,  barnacle 


A  SMALL  SHARK. 
Photographed  under  water. 


250 


•FIRST   YEAR   SCIENCE 

' 


Fig.   110. 


and  coral  polyp,  are  fixed,  and  rely  upon  the  currents  of 
the  water  to  bring  them  their  food,  while  others,  like  the 
crab,  the  lobster  and  the  fish,  'move  from  place 
to  place  in  search  of  prey. 

In  the  warmer  seas  the  surface  water  is  often 
filled  with  minute  microscopical  animals  which 
have  the  power,  when  disturbed,  of  emitting 
light,  so  that  when  a  boat  glides  through  these 
waters,  a  trail  of  sparkling  silver  seems  to  fol- 
low in  the  wake. 

Between  the  surface  and  the  bottom  of  the 
-deep  ocean  there  seems  to  be  a  vast  depth  of 
water  almost  devoid  of  life.  This  region,  .like  the  bot- 
tom of  the  ocean,  has  been  little  explored  and  there  may 
be  life  here  which  has  not  been  discovered.  From  the 
bottom  of  the  sea  the  dredge  has  brought  up  some  very 
curious  forms  of  life.  Here  under  tremendous  pressure 
and  in  profound  darkness  have  been  developed  species  of 
carnivorous  fishes. 

Some  of  these  have 
large  peculiarly  well- 
developed  eyes  and 
others  have  not  even 
the  rudiments  of  eyes. 
As  the  light  of  the  sun 
never  penetrates  to  these 
depths,  it  would  seem 
at  first  that  eyes  could 
be  of  no  use  to  animals, 
but  it  has  been  found 
that  some  of  the  ani- 
mals of  the  ocean  bottom  have  the  power  of  emitting 
light  in  some  such  way  as  the  glowworm  and  firefly  do, 
and  it  is  probable  that  it  is  to  see  this  phosphorescent 


FLYING  FISH. 

Notice  how  the  front  fins  have  become 
wing-like. 


LIFE  OF  THE  LAND 


251 


light  that  the  eyes  of  the  animals  are  used.  There  are 
no  plants  here  and  the  life  is  much  less  abundant  and  less 
varied  than  near  the  surface. 

There  is  but  little  variation  in  the  conditions  surround- 
ing the  animals  of  the  sea,  so  the  organs  corresponding 
to  these  conditions  are  not  diverse.  Living  in  a  buoyant 
medium  dense  enough  to  support  their  bodies,  and  of 
almost  unvarying  tem- 
perature, the  sea  ani- 
mals have  never  re- 
quired or  developed 
varied  organs  for  loco- 
motion, like  the  wing, 
the  hoof  and  the  paw, 
or  for  protection  from 
cold,  like  the  feather, 
the  hair,  or  wool.  It 
is  true  that  certain  sea 
dwellers,  like  the  seal, 
are  covered  with  hair, 
but  these  air  breathers  were  probably  originally  a  land  type 
and  have  acquired  the  habit  of  living  in  the  water.  The 
highest  traits  of  animal  life,  such  as  are  found  in  land 
animals,  have  not  been  required  or  acquired  by  the  sea 
animals,  and  although  the  number  of  species  and  kinds  is 
very  great,  there  is  not  found  among  them  the  same  grade 
of  intelligence  or  'power  of  adaptability,  as  among  the 
land  animals. 

116.  Life  of  the  Land  —  The  highest  development  of  both 
plant  and  animal  life  is  found  upon  the  land.  Here  at 
the  meeting  place  of  the  solid  earth  and  its  gaseous  en- 
velope, subjected  to  great  variations  in  amount  of  sun- 
light, moisture,  temperature  and  soil,  the  plants  and 
animals  have  acquired  a  marvelous  variety  of  forms  and 


SEALS. 
Originally  land  animals. 


252 


FIRST    YEAE   SCIENCE 


structures    to    adapt    them    for    their    varied    surround- 
ings, and  enable  them  to  secure  a  living. 

Some  plants  lift  their  strong 
arms  high  into  the  air  to  in- 
tercept the  sunbeams  before 
they  strike  the  earth,  while 
others  clothe  the  surface  with 
a  dress  of  varied  green.  In 
some  plants,  odor,  nectar  or 
juicy  berries  attract  the  animals 
whose  aid  is  needed  for  fertiliz- 
ing and  scattering  their  seeds, 
while  in  others,  noxious  odors, 
prickles,  thorns  and  acrid  secre- 
tions warn  away  animals  de- 
structive to  their  welfare.  The 
high- 


PRICKLY  PHLOX. 

Notice  the  thorns  by  which  it 

protects  itself. 


est  perfection  of  beauty,  utility 
and  productiveness  among 
plants  has  been  reached  by 
those  of  the  land. 

The  animals  of  the  land, 
surrounded  by  the  air,  which 
bears  no  food  solutions  to  inert 
mouths,  must  be  well  endowed 
with  the  power  of  motion  in 
order  to  procure  their  food. 
They  must  either  crawl  over 
the  surface  or  be  provided  with 
appendages  to  support  their 
weight  against  gravity.  There 
is  no  floating  supinely  in  the 
air  as  in  the  water.  Movement,  exertion,  search  are  the 
requisites  of  this  realm.  The  eggs  and  young,  as  a  rule, 


BIRD'S  NEST. 
A  simple  home. 


LIFE   OF  THE  LAND 


253 


cannot  be  cast  adrift  to  hatch  and  care  for  themselves; 
the  nest,  the  burrow,  the  den  must  be  provided.  This  is 
the  realm  of  homes. 

The  land  animals  are  also  the  most  intelligent.  Birds 
long  ago  solved  the  problem  of  flight  for  a  body  heavier 
than  air,  which  is  now  being  successfully  solved  by  man 
after  years  of  effort.  Certain  animals,  like  the  bee,  the 
ant  and  the  squirrel,  have  the  provident  habit  of  storing 
up  food  in  the  summer  against  a  day  of  need.  Other  ani- 
mals, like  the  birds,  have  learned  to  migrate  to  a  warmer 


A  BKAVER  DAM. 
Notice  the  two  beavers  on  top  of  the  dam. 

clime  when  winter  comes.  The  beaver  is  probably  the 
pioneer  in  hydraulic  engineering.  When  he  feels  the  need 
of  a  water  reservoir,  he  builds  a  dam  and  makes  it.  To- 
day many  a  swamp  in  the  northern  states  owes  its  origin 
to  him.  Wonderful  indeed  is  the  intelligence  of  many  of 
the  land  animals,  due  in  large  part  to  their  development 
amid  varied  geographical  conditions. 


254 


FIRST   YEAR   SCIENCE 


117.  Distribution  of  Animals.  —  An  examination  of  a  globe 
shows  (1)  that  the  land  is  massed  around  the  north  pole, 
(2)  that  the  three  continental  masses  to  the  south  are 
separated  from  each  other  by  wide  seas,  and  (3)  that 
while  two  of  these  are  connected  by  narrow  strips  of 
land  to  northern  continents,  the  third  is  entirely  sepa- 
rated from  all  other  land. 

But  slight  changes  in  elevation  would  connect  the 
northern  continents  with  each  other.  As  they  are  so 
closely  related  to  each  other,  it  might  be  expected  that 
the  animals  of  these  continents  would  resemble  each  other, 

particularly  in  the  more 
northern  parts.  This 
is  true.  Bears,  wolves, 
foxes,  elk,  deer  and 
sheep  of  nearly  related 
species  are  found  dis- 
tributed over  the  north- 
ern continents. 

The  animals  of  the 
southern  continents  are 
much  less  nearly  re- 
lated. The  ostrich, 
giraffe,  zebra  and  hip- 
popotamus are  among 


OSTRICHES. 
The  largest  of  all  birds. 

the  characteristic  animals  of  Africa  which  are  not  found 
elsewhere.  In  South  America  the  tapir,  great  ant  eater, 
armadillo  and  llama  are  among  the  animals  not  represented 
elsewhere.  Both  of  these  continents,  however,  have  ani- 
mals closely  related  to  those  of  other  great  divisions, 
showing  that  their  present  isolation  has  not  continued  far 
back  in  geological  time. 

The  animals  of  Australia  differ  greatly  from  those  of 
the  other  continents.     The  quadrupeds  here  are  marsur 


DISTEIBUTION   OF  ANIMALS 


255 


piala,  animals  which  usually  carry  their  young  in  a  pouch. 
The  only  members  of  the  family  existing  at  present  else- 
where are  the  American 
opossums.  The  largest 
of  the  marsupials  is  the 
great  kangaroo  which 
measures  between  seven 
and  eight  feet  from  its 
nose  to  the  tip  of  its 
tail.  Although  it  has 
four  feet,  yet  it  runs 
by  making  extraordi- 


OPOSSUM. 

Many  opossums  have  no  pouch  but  carry 
their  young  on  their  backs. 


nary  leaps  with  its  strong 
hind  feet.  Here  is  also 
found  one  of  the  most  singular  of  all  living  animals,  the 


A  KANGAROO  FEEDING. 
Notice  the  peculiar  position  it  is  forced  to  take  because  of  its  short  front  legs. 


256 


FIRST   YEAR   SCIENCE 


duckbill,  the  lowest  of  all  quadrupeds,  which  in  its  char- 
acteristics resembles  both  quadrupeds  and  birds. 

All  this  seems  to  show  that  the  distribution  and  devel- 
opment of  the  animals  of  the  different  continents  have  been 
largely  dependent  upon  the  former  geographical  relations 
of  the  land  masses.  The  native  animals  of  a  region  are 
not  necessarily  the  only  ones  suited  to  it ;  animals  from 
other  places  may  be  even  better  adapted,  but  they  have 
been  kept  out  by  some  natural  barrier.  This  is  particu- 
larly evident  in  the  case  of  Australia,  where  the  weak 
native  animals  would  have  been  readily  displaced  by  the 
stronger  animals  of  Asia  could  these  have  reached  that 
isolated  continent. 

118.  Life  as  Affected  by  Climate.  —  Climate  has  had  a 
great  effect  upon  the  distribution  and  development  of  life. 


TIMBER  LINE  ON  A  HIGH  MOUNTAIN. 

But  the  life  on  the  earth  cannot  be  grouped  into  climatic 
belts,  as  certain  animals  and  plants  are  able  to  endure  a 


LIFE  AS  AFFECTED  BY  CLIMATE 


257 


wide  range  of  climatic  conditions.  Moisture,  sunlight 
and  temperature  are  the  chief  factors  which  determine  the 
growth  and  development  of  plants.  If  the  temperature  is 
too  high  or  too  low,  they  cannot  exist.  If  sunlight  or 
moisture  is  wanting,  they  cannot  build  their  tissues. 

In  regions  where  the  temperature  is  constantly  below 
freezing,  there  can  be  no  plant  life.  Where  the  tempera- 
ture is  above  freezing  for  only  a  short  time  in  the  year, 
plant  growth  is  slight  and  whatever  plants  there  are  must 
be  small  and  stunted.  Only  where  there  is  a  long  grow- 


AN  OASIS  IN  THE  MOJAVE  DESERT. 


MESQUIT  BEANS. 
From  this  desert  plant  some  In- 
dian tribes  made  their  bread. 

ing    period    can     large 

plants    exist.      That    is 

why  there  is  almost   no 

plant  and  therefore  almost  no  animal  life  on  the  upper 

parts  of  lofty  mountains,  while  somewhat  farther  down 

the  life  is  stunted,  and  still  lower  down  life  flourishes. 

Changes  in  latitude  have  the  same  effect. 

Where  moisture  is  lacking,  no  plants  can  grow.     Where 
there  is  but  little  moisture,  only  those  plants  can  grow 


258  FIRST  TEAR.  SCIENCE 

which  are  able  to  make  the  best  possible  use  of  the  avail- 
able moisture.  In  dry  regions  the  plants  are  few  and  so 
constructed  that  little  moisture  can  be  evaporated  from 
them.  In  dry  desert  regions,  except  where  water  finds  its 
way  to  the  surface  in  considerable  quantity,  forming  oases, 
there  can  be  but  little  forage  for  animals,  and  what  there 
is,  is  scattered.  The  desert  animal  must  therefore  be  a 
wanderer,  able  to  subsist  upon  meager  fare. 

This  is  true  of  the  human  inhabitants  of  the  desert  as 
well.     They  must  rove  about  in  small  bands  living  in 


A  WATER  HOLE  IN  THE  DESERT. 

tents,  picking  up  a  precarious  living  for  themselves  and 
their  animals,  and  they  must  be  hardy  and  capable  of 
withstanding  privation.  They  must  move  rapidly  and 
carefully  over  the  long  distances  separating  the  patches 
where  food  can  be  found.  They  must  therefore  be  fine 
horsemen,  like  the  Arabs  of  Arabia  and  the  Sahara,  or 
strong  and  swift  runners,  like  the  Indians  of  the  south- 
western United  States. 

The  life  of  man  on  the  oases,  although  much  less  miser- 
able than  that  on  the  desert,  is  subject  to  great  disadvan- 


LIFE  AS  AFFECTED  BY  CLIMATE  259 

tages.  These  spots  are  of  limited  extent  and  frequently 
of  limited  moisture.  They  are  often  separated  by  almost 
untraversable  areas  from  the  other  inhabitants  of  the  world. 
There  can  be  but  little  commerce  or  intercourse  with  the 


A  DESERT  AND  OASIS. 
Notice  the  oasis  at  the  foot  of  the  gully  where  a  spring  comes  to  the  surface. 

rest  of  mankind.  Although  the  oasis  may  appeal  with  a 
poetic  charm  to  the  dweller  in  the  desert,  yet  to  the  inhab- 
itant of  a  fertile  country  it  is  but  a  sorry  place. 

In  regions  where  there  is  plenty  of  moisture,  sunlight 
and  heat,  the  growth  of  plants  and  animals  is  abundant  and 
is  only  limited  by  space  and  food.  Here  life  is  at  its  best. 


260 


FIRST   YEAR   SCIENCE 


119.  Life  on  Islands.  —  Islands  which  rise  from  the  conti- 
nental shelves  were  probably  at  one  time  connected  with 
the  continents,  but  have  since  been  separated  by  the  sub- 
mergence of  the  intervening  lowland.  The  animals  and 
plants  of  such  islands  are  similar  to  those  of  the  adjacent 
large  land  masses.  But  oceanic  islands  possess  only  those 
types  of  plants  and  animals  which  originally  were  able  to 
float  or  fly  to  them  over  the  surrounding  'water  expanse. 
Indigenous  mammals,  except  certain  species  of  bat,  are 
wanting.  Birds  are  abundant. 

On  the  tropical  islands  the  cocoanut  palm  is  the  main 
supply  of  vegetable  food,  clothing  and  building  material. 
Many. of  the  species  of  both  plants  and  animals  are  differ- 
ent from  those  of  the  nearest  continent  and  even  of  the 
adjacent  islands.  So  complete  has  been  the  isolation  of 

the  life  of  these  islands 
for  so  long  a  time 
that  it  has  been  possible 
for  great  differences  in 
species  to  develop.  Large 
unwieldy  birds  unable 
to  fly  or  run  rapidly 
have  been  found  on  some 
oceanic  islands,  the  dodo 
of  Mauritius,  now  ex- 
tinct, being  one  of  the 
most  notable. 

The  absence  of  pred- 
atory animals  has  probabty  made  the  development  of  such 
forms  possible.  The  great  species  of  tortoise  from  the  Gala- 
pagos Islands  perhaps  owes  its  development  to  the  same 
cause.  Nowhere  else  have  such  huge  tortoises  been  found. 
The  remarkable  fauna  and  flora  found  on  oceanic  islands 
may  be  regarded  as  due  to  their  geographical  isolation. 


THE  DODO. 

Although  the  dodo  is  extinct,  sufficient 

remains  have  been    found    to    enable 

scientists  to  tell  how  it  looked. 


LIFE  AS  AFFECTED  BY  MAN  261 

120.  Life  as  Affected  by  Man.  —  Wherever  man  has  es- 
tablished himself,  he  has  become  a  dominant  factor  in  the 
distribution  and  existence  of  plants  and  animals.  For- 
ests are  cut  down,  swamps  are  drained  and  streams 
dammed.  Shade-loving  plants  suddenly  find  themselves 
exposed  to  the  full  glare  of  the  sun,  plants  which  need 
much  water  find  themselves  in  a  dry  soil,  and  other  plants 
which  need  a  dry  soil  are  flooded  by  the  impeded  streams. 
They  cannot  stand  these  sudden  changes  of  environment 


ORIGINAL  FLORA  SUPPLANTED  BY  NEW  PLANTS. 

and  die  out.  The  plow  overturns  the  sod  and  the  fields 
are  sown  with  seeds  the  natural  home  of  which  may  have 
been  thousands  of  miles  away  across  the  sea. 

In  the  course  of  years  the  original  flora  of  the  region  is 
represented  by  only  a  few  species  inhabiting  places  man 
has  not  deemed  it  worth  his  while  to  cultivate.  New 
plants  suited  to  man's  wants  have  taken  the  place  of  those 
which  through  thousands  of  years  of  struggle  have  shown 
themselves  the  best  adapted  to  the  geographical  conditions 
in  the  region. 


262 


YEAR   SCIENCE 


The  animals  share  the  same  fate  as  the  plants.  Domes- 
tic animals  replace  the  wild  denizens  of  the  country. 
Only  in  inaccessible  and  waste  places  are  a  few  lone  rem- 
nants of  the  native  fauna  left.  If  the  area  which  man 
enters  is  limited  and  bounded  by  impassable  barriers,  as  in 
the  case  of  islands,  certain  animals  may  be  entirely  exter- 
minated, as  wolves  and  bears  have  been  in  England.  If 
the  animal  is  a  unique  species,  its  extermination  from  its 
native  island  may  mean  its  total  destruction,  as  in  the 
case  of  the  dodo  of  Mauritius. 

121.  Forestry.  —  One  of  the  notable  ways  in  which  mod- 
ern man  has  affected  the  life  and  industries  of  the  earth  is 


BAD  FORESTRY. 

The  debris  was  left  to  feed  the  forest  fires,  and  all  the  standing  timber 
was  ruined. 

in  his  treatment  of  the  forests.  In  North  America,  be- 
fore the  coming  of  the  white  man,  there  were  probably 
extensive  areas  where  the  growth  of  forests  had  been 
checked  by  fires  set  by  the  Indians.  The  prairie  regions 
were  probably  much  enlarged  by  the  annual  grass  fires. 


FORESTRY 


263 


Tree-covered  areas,  too,  were  often  burned  over,  and  the 
growth  of  the  trees  checked,  in  order  to  make  hunting  less 
difficult.  The  greater  part  of  the  country  was,  however, 
covered  with  thrifty  forests. 

In  recent  years  the  denrand  for  lumber  and  wood  pulp 
and  the  careless  and  wasteful  way  in  which  the  forests 
have  been  handled  by  the  lumbermen  has  greatly  reduced 
the  forests  of  the  United  States.  It  has  been  authorita- 
tively stated  that  if  the  present  waste  of  our  forest  land 


BAD  FORESTRY. 
The  forest  was  razed,  leaving  no  small  trees  for  future  growth. 

continues,  the  timber  supply  of  the  Country  will  be  ex- 
hausted before  1940.  Not  only  are  the  forests  being  reck- 
lessly cut  down,  but  forest  fires  are  each  year  destroying 
millions  of  dollars  worth  of  timber.  When  the  impor- 
tance of  lumber  to  all  kinds  of  industries  is  considered, 
the  rapid  exhausting  of  our  forest  supplies  becomes  al- 
most appalling. 

But  not  only  is  the  destruction  of  the  forests  a  men- 
ace to  the  industries  in  which  lumber  is  necessary,  but 
the  effects  are  far  reaching  in  many  other  directions. 


264 


FIItST   YEAR   SCIENCE 


Slopes  from  which  the  forests  have  been  removed  become 
an  easy  prey  to  the  forces  of  erosion,  and  the  soil  which 
for  thousands  of  years  has  been  accumulating  may  be 
swept  away  by  the  rainfall  of  a  few  seasons,  leaving  the 
slopes  bare  of  soil  and  devoid  of  vegetable  life.  Thus  the 


BAD  FORESTRY. 
The  hillside  was  stripped,  leaving  it  a  prey  to  erosion. 

sites  of  valuable  forests,  which  by  proper  care  might  have 
been  continual  wealth  producers,  are  rendered  nearly 
profitless  deserts. 

The  harmfulness,  however,  does  not  stop  here.  The 
rain  that  falls  upon  these  slopes,  and  which  was  formerly 
retained  by  the  roots  and  vegetation,  so  that  it  slowly 
crept  downward  into  the  valleys  and  streams,  now  runs 
off  quickly,  flooding  the  rivers  and  doing  damage  to 
regions  at  a  distance.  Streams  which  formerly  varied 


FORESTRY 


265 


but  little  in  their  volume  during  the  entire  year,  now  be- 
come subject  to  great  extremes  of  high  and  low  water. 
This  renders  them  less  useful  for  manufacturing,  com- 
merce and  water  supply  to  say  nothing  of  the  frightful 
damage  done  each  year  by  floods. 

The  destruction  of  the  forests  tends  also  to  extermi- 
nate the  wild  animals  and  deprives  man  of  a  chance 
to  get  away  from  his 
artificial  surroundings 
and  obtain  a  knowledge 
and  an  enjoyment  of 
life  and  nature  which 
has  been  unaffected  by 
his  own  dominant  in- 
fluence. 

In  many  European 
countries  the  forests 
have  become  a  national 
care  and  not  only  is  the 
cutting  of  trees,  except 
under  certain  restric- 
tions, prohibited,  but 
the  greatest  care  is 
maintained  to  guard 
against  fires.  In  our 
own  country  the  gov- 
ernment has  recently  established  a  number  of  forest 
preserves  which  are  carefully  patrolled,  and  here  the  de- 
struction from  forest  fires  is  rigidly  guarded  against. 
Great  care  of  all  forests  should  be  taken  by  hunters, 
campers  and  all  others  who  visit  them,  and  also  by  the 
railways  passing  through  them.  Loggers  and  lumber- 
men should  see  that  it  is  to  their  interest  to  maintain 
growing  forests  and  not  wantonly  to  destroy  them. 


GOOD  FORESTRY. 

Notice  how  carefully  the  underbrush  has 
been  removed  to  guard  against  tire. 


266 


FIRST  YEAR   SCIENCE 


When  the  native  forests  are  destroyed,  trees  of  other 
kinds  may  in  time  replace  those  removed,  but  frequently 
these  are  of  less  commercial  value.  Thi>s,  when  the  coni- 
fer forests  of  the  northern  states  are  cut  off,  birches  and 


GOOD  FORESTRY. 
Notice  how  the  underbrush  and  small  limbs  have  been  cleaned  up. 

poplars  replace  them.  If  only  the  larger  trees  had  been 
cut,  leaving  the  smaller  and  younger  trees  to  hold  the 
ground,  the  more  valuable  forests  might  have  been  re- 
tained. 

122.  Flora  of  the  United  States.  —The  United  States  has 
such  a  great  range  of  climate,  soil,  elevation  and  other 
geographical  conditions  that  it  possesses  a  large  variety 
of  plants.  About  five  hundred  different  kinds  of  native 
trees  have  been  listed,  and  there  are  many  different  kinds 
of  shrubs  and  smaller  plants.  To  these  native  plants 
must  be  added  many  useful  as  well  as  ornamental  plants 


FLORA   OF  THE   UNITED   STATES 


267 


and  not  a  few  noxious  weeds,  which  have  been  imported 
from  other  countries  and  have  found  an  agreeable  home 
here. 

The  largest  and  perhaps  most  remarkable  trees  in  the 
United  States  are  the  Big  Trees  of  California,  a  species  of 
redwood.  Trees  of  this  species  have  been  measured  which 


A  CALIFORNIA  Bia  TREE. 
Notice  the  size  at  the  base. 

were  325  ft.  high,  more  than  100  ft.  higher  than  Bunker 
Hill  Monument,  and  others  which  were  more  than  90  ft. 
in  circumference.  A  plant  which  has  probably  appro- 
priated more  territory  than  any  other  plant  in  the  world 
is  the  "sage  brush"  of  the  arid  western  plains.  These 
low  grayish  shrubs  cover  hundreds  of  thousands  of  square 
miles.  They  are  useless  except  for  fuel.  In  the  well- 


268 


FIRST   YEAR   SCIENCE 


watered  part  of  the  country,  plants  are  abundant  and 
varied,  ranging  from  the  subtropical  palms  of  the  Gulf 
coast  to  the  semi-arctic  types  of  the  northern  border. 

123.  Fauna  of  the  United  States.  —  As  the  wide  treeless 
plains  and  prairies  of  the  central  part  of  the  country  con- 
tained few  coverts  for  skulking  animals  of  prey,  they  were 
admirably  adapted  to  the  wants  of  gregarious  grazing 
animals.  Here  were  found  the  countless  herds  of  ante- 
lopes and  buffaloes  which  in  the  early  days  of  transcon- 
tinental travel  swarmed  over  the  territory  crossed  by  the 
railroads  and  not  infrequently  forced  the  trains  to  stop 
and  wait  until  they  had  crossed  the  track.  To-day  they 
are  almost  exterminated. 

The  forests  of  the  northern  regions  with  their  grassy 
glades  and  meadows,  once  the  home  of  great  herds  of 

caribou  and  great  numbers  of 
moose,  have  too  frequently  re- 
sounded to  the  sound  of  ax  and 
gun  still  to  contain  many  of 
these  noble  creatures. 

Among  the  mountains  with 
their  rough  surfaces  and  rugged 
fastnesses  the  black,  brown, 
and  grizzly  bear  once  roamed 
supreme,  but  now  they  find 
security  only  in  the  most  inac- 
cessible places.  Wolves  once 
skulked  in  bands  far  and  wide 
over  almost  the  entire  country, 
ready  to  pull  down  and  devour 
weaker  animals,  but  now  both  they  and  their  prey  have 
almost  vanished. 

The  fur-bearing  animals  which  inhabited  the  streams 
and  dales  and  whose  valuable  pelts  tempted  the  early 


COYOTE. 

The  prairie  wolf  of  the  western 
plains. 


SUMMARY 


269 


hunters  to  explore  the  unknown  regions  of  the  country 
and  mark  out  the  trails  afterward  followed  by  the  pio- 
neers, have  almost  en- 
tirely    disappeared. 
Small  animals,  like  the 
fox,  the  prairie  dog,  the 
skunk,  the  woodchuck, 
still  remain,    the   puny 
survivors     of     a     once 
varied  fauna.    Plain  and 
valley,  hill  and    moun- 
tain are  at  present  nearly  PRAIRIE  DOG. 
devoid   of   their  native 

inhabitants.     The  horse,  the  cow,  the  mule  are  the  chief 
members  of  the  present  fauna. 

Summary.  — Physical  conditions  have  a  great  effect  on 
the  distribution  of  life  upon  the  earth.  It  is  hard  for  liv- 
ing things  to  cross  high  mountains,  broad  oceans  or  vast 
deserts.  When  confined  to  certain  climates  and  areas, 
plants  and  animals  naturally  adjust  themselves  to  these. 

Life  in  the  sea  is  so  simple  that  plants  and  animals 
there  are  not  forced  to  become  as  highly  developed  as  are 
those  of  the  land.  On  land  there  are  greater  ranges  of 
climate  and  other  physical  conditions,  so  that  plants  and 
animals  have  been  forced  to  a  high  development  in  order 
to  survive.  Probably  the  two  greatest  forces  affecting 
land  life  are  climate  and  man.  Man  transplants  and 
transports  animals  and  plants  according  to  his  desires. 
The  physical  conditions  decide  whether  or  not  they 
shall  live. 

By  his  treatment  of  forests  man  can  also  have  a  great 
effect  upon  the  wealth  and  beauty  of  the  country,  upon  the 
safety  of  its  rivers  and  the  reliability  of  its  water  power. 


270  FIRST   YEAR   SCIENCE 

*      .  v** 

Much  more  money  has  been  lost  in  the  United  States 
through  the  floods  and  fires  caused  by  bad  forestry  than 
haas  been  gained  by  the  people  who  cut  the  trees. 

Because  of  the  wide  range  of  climate  and  the  variety  of 
physical  conditions,  there  are  a  great  many  different  kinds 
of  plants  and  animals  in  the  United  States,  but  the  wild 
animals  have  been  steadily  killed  off  as  man  has  needed 
their  haunts  for  his  farms  and  dwellings. 

QUESTIONS 

What  do  the  rock  layers  show  in  regard  to  the  history  of  life  ? 

Give  several  reasons  why  the  same  kind  of  plants  and  animals  are 
not  found  all  over  the  earth. 

What  animals  do  you  know  that  are  peculiarly  adapted  to  the  con- 
ditions under  which  they  live  ? 

If  you  could  take  a  trip  in  a  submarine  capable  of  traveling  over 
and  through  the  sea,  what  kind  of  animals  would  you  expect  to 
find  ?  Under  what  different  conditions  would  these  animals  be  living  ? 

How  are  land  animals  prepared  to  meet  the  conditions  about 
them? 

Describe  how  the  distribution  of  animals  has  been  influenced  by 
geographical  conditions. 

How  are  animals  affected  by  climate  ? 

What  influence  have  oceanic  islands  had  on  life? 

How  has  man  in  many  places  changed  the  life  of  the  land? 

Why  is  the  proper  care  of  forests  so  important  to  the  well  being  of 
man? 

To  what  plants  and  animals  is  the  United  States  the  "  home  land  "? 


CHAPTER   VIII 

THE  SEA 

124.  The  Sea.  —  On  looking  at  a  map  of  the  world  or  at  a 
globe,  one  is  immediately  impressed  by  the  predominance 
of  the  sea.  The  whole  area  of  the  globe  is  about 
196,940,000  square  miles,  72%  of  which  is  water.  The 


THE  OCEAN. 
From  a  photograph  taken  in  mid-Atlantic. 

larger  part  of  the  land  is  in  the  northern  hemisphere,  and 
of  the  water  in  the  southern  hemisphere.  A  compara- 
tively small  land  area  extends  below  40°  south  latitude, 
about  the  latitude  of  Philadelphia  in  the  northern  hemi- 

271 


272  FIRST  YEAR   SCIENCE 

sphere.  Most  of  the  maps  of  the  world  do  not  represent 
the  southern  hemisphere  below  latitude  60°,  which  is 
about  the  latitude  of  Petrograd  (St.  Petersburg)  in  the 
northern  hemisphere.  Thus  the  equator  is  usually  con- 
siderably below  the  center  of  the  map. 

125.  Divisions  of  the  Sea.  —  Although  most  of  the  surface 
water  of  the  earth  is  connected,  yet  for  many  purposes  it 
is  better  to  put  this  water  area  into  somewhat  arbitrary 
divisions.     We  thus  speak  of   the  Atlantic,  the   Pacific, 
the  Indian  ocean,  each  of  which  may  be  divided  by  the 
equator  into   a  northern  and  a  southern  part,  and   the 
Arctic  and  Antarctic  oceans  which  surround  either  pole. 
Sometimes  a  division  is  made  from  the  parallel  40°  south 
a,nd  this  great  body  of  water,  almost  without  land  boun- 
daries is  called  the  Southern  Ocean. 

The  boundaries  of  these  oceans  are  irregular  in  shape, 
but  with  the  exception  of  the  great  Southern  Ocean  and 
of  the  Arctic  Ocean,  which  is  really  an  inclosed  sea, 
they  narrow  toward  the  north.  They  have  a  number  of 
partially  landlocked  seas  connected  with  them.  In  some 
instances  these  penetrate  far  into  the  land,  as  in  the  cases 
of  the  Mediterranean  Sea  and  Gulf  of  Mexico.  The  sur- 
face of  the  sea  is  level,  unstable,  easily  moved  and  always 
rising  and  falling  in  rapid  and  changeful  undulations. 

126.  Continental  Shelf.  —  Around  the  border  of  the  con- 
tinents and  of  those  islands  which  are  near  the  continents, 
there  extends,  in  some  cases  to  a  distance  of  two  or  three 
hundred  miles,  a  gradually  deepening  ocean  floor.     This 
gradually  deepening  border  is  called  the  continental  shelf. 
When  this  floor  has  reached  the  depth  of  about  600  feet, 
the  gradual  slant  suddenly  changes  into  a  quick  descent 
to  the  depths  of  the  ocean,  two  or  three  miles. 

Upon  this  shelf  lie  the  great  continental  islands,  like 
the  British  Isles  and  the  East  Indies.  It  is  this  that  fur- 


COMPOSITION  OF  OCEAN    WATEES 


273 


nishes  the  great  fishing  banks  of  the  earth,  such  as  the 
Grand  Banks  of  Newfoundland  and  those  around  Iceland 
and  the  Lofoten  Islands,  where  fishermen  for  ages  have 
obtained  vast  supplies  of  fish.  There  is  no  equal  area  of 
the  earth  where  the  life  is  so  varied  and  the  struggle  for 
existence  so  great  as  on  these  shallow  continental  borders. 


CONTINENTAL  SHELF. 
A  model  showing  the  sea  floor  off  the  coast  of  Southern  California. 

Here  the  mud  and  sand  brought  down  by  the  rivers  is 
spread  out  and  the  sedimentary  rocks  formed.  It  is  the 
elevation  of  this  shelf  which  has  formed  the  low-lying 
coastal  plains  which  border  many  of  the  continents. 
There  is  good  reason  to  believe  that  the  deep  floors  of  the 
sea  have  never  been  raised  into  dry  land,  and  that  the 
vast  extent  of  sedimentary  rocks  which  make  up  the  larger 
portion  of  the  land  has  almost  all  been  laid  down  in  re- 
gions which  were  at  the  time  continental  shelves. 

127.   Composition  of  Ocean  Waters.  —  Experiment  122.  — Into 

a  dish  of  fresh  water  put  a  demonstration  hydrometer  or  stick  such  as 


274  FIRST   YEAR   SCIENCE 

was  used  in  Experiment  35.  Mark  the  depth  to  which  it  sinks. 
Place  the  hydrometer  now  in  sea  water  and  mark  the  depth  to  which 
it  sinks.  If  sea  water  cannot  be  obtained,  dissolvejn  a  pint  of  fresh 
water  about  15  g.,  or  half  an  ounce,  of  salt.  This  will  give  the  water 
about  the  same  amount  of  dissolved  solid  material  as  sea  water  would 
have.  About  how  much  more  of  its  length  does  the  hydrometer  sink 
in  fresh  water  than  in  sea  water  ?  Will  a  piece  of  ice  project  more 
out  of  salt  water  than  it  would  out  of  fresh  water  ? 

Experiment  123.  —  If  ocean  water  can  be  obtained,  boil  down  about 
a  pint  of  it  in  an  open  dish.  Taste  of  the  residue  which  is  left. 
What  is  the  principal  constituent  of  this  residue  ? 

There  is  probably  no  water  on  the  surface  of  the  earth 
which  is  absolutely  pure.  Water  is  the  greatest  solvent 
known,  and  it  dissolves  to  a  greater  or  less  extent  almost 
all  substances  with  which  it  comes  in  contact.  When  the 
rivers  run  into  the  sea,  they  carry  with  them  whatever 
their  water  has  dissolved  from  the  land,  and  when  the  sun 
evaporates  the  water,  and  it  is  borne  away  again  to  fall 
upon  the  land,  the  dissolved  material  is  left  behind  in  the 
ocean. 

Thus  the  sea  has  for  all  time  been  receiving  the  soluble 
contributions  from  the  land.  It  is  easy  to  prove  that  it 
contains  salt,  for  we  can  taste  it.  It  must  contain  lime, 
for  corals  and  shell  animals  depend  upon  this  for  the 
hard  parts  of  their  bodies.  There  must  be  organic  food 
material  in  it,  or  else  fixed  animals  like  oysters  could  not 
get  food.  It  contains  air,  for  without  air  fishes  could  not 
breathe.  These  are  the  principal  substances  which  we 
need  to  consider  in  the  study  of  the  ocean  water,  but  the 
chemist  can  find  many  other  substances  dissolved  in  it. 
On  account  of  the  materials  dissolved,  sea  water  weighs 
more  than  fresh  water,  or  has  a  greater  specific  gravity. 
A  cubic  foot  of  fresh  water  weighs  about  62.5  Ibs.  whereas 
a  cubic  foot  of  sea  water  weighs  over  64.25  Ibs. 


CONDITION  OF  THE  OCEAN  FLOOR  275 

128.  Ocean  Depths.  —  The  greatest  depth  thus  far  found 
in  the  ocean  is  nearly  six  miles.     This  was  found  in  the 
Pacific  Ocean  near   the   Ladrone  Islands.     The  greatest 
depth  in  the  Atlantic  Ocean  thus  far  discovered  is  a  little 
over  five  miles  at  a  point  north  of  Porto  Rico.     The  aver- 
age depth  of  the  sea  is  probably  about  two  and  one  half 
miles. 

Although  the  pressure  at  the  bottom  of  the  ocean  must 
be  tremendous,  yet  so  incompressible  is  water  that  a  cubic 
foot  of  it  weighs  but  little  more  at  the  bottom  of  the  sea 
than  it  does  at  the  top.  Thus  a  body  which  sinks  will  in 
time  reach  the  bottom  no  matter  what  the  depth  may  be. 
At  a  depth  of  two  miles  the  pressure  is  over  300  times  as 
much  as  at  the  surface  of  the  water  and  here,  as  we  have 
already  found,  it  is  about  15  pounds  to  the  square  inch. 

If  a  bag  of  air  which  had  a  volume  of  300  cubic  inches 
at  the  surface  were  sunk  in  the  ocean  to  a  depth  of  two 
miles,  it  would  have  a  volume  of  less  than  a  cubic  inch, 
and  the  pressure  upon  it  would  be  about  2  J  tons.  It  thus 
happens  that  deep  sea  fishes  when  brought  to  the  surface 
have  the  air  in  their  swimming  bladders  so  expanded  that 
the  bladder  is  often  blown  out  of  their  mouths. 

129.  Condition  of  the  Ocean  Floor.  —  The  ocean  floor  is  a 
vast,    monotonous,    nearly   level   expanse   whose   dreary, 
slimy  and 'almost  lifeless  surface  is  enveloped  in  never- 
ending  night  and   is   pressed  upon  by  a  vast  weight  of 
stagnant,  frigid  water.     Here   and   there  volcanoes  rise 
upon  it  with  gradually  sloping,  featureless  cones,  and  some- 
times a  broad  wavelike  swell  reaches  within  a  mile  or  so 
of  the  surface.     Such  a  swell  extends  along  the  center 
of  the  Atlantic  Ocean  through  Ascension  Island  and  the 
Azores. 

There  are  no  hills  and  vales,  no  mountain  ranges  having 
sharp  peaks  and  deep  valleys.  Gradually  rising  ridges 


276 


FIRST   YEAR   SCIENCE 


and  volcanoes,  sometimes  topped  with  coral  islands,  alone 
vary  the   monotony.     It   is   the   nether  world  of  gloom 

and  unaltering  sameness. 
Here  the  derelicts  of 
ages  past,  after  their 
fierce  buffeting  with 
wind  and  wave,  have 
found  a  quiet,  change- 
less haven  where  they 
may  lie  undisturbed  un- 
til absorbed  into  the 
substance  of  the  all-en- 
folding water.  Some 
animal  species  which 
lived  in  the  light  of 
former  geological  ages 
have  here  found  a  rest- 
ing place  where  the 
strife  of  progress  is 
stilled  and  the  laggard 
in  the  race  of  develop- 
ment may  live  in  peace. 
130,  The  Carpet  of  the  Ocean  Floor.  —  Near  the  shore,  the 
floor  of  the  ocean  is  covered  with  sand  and  mud  derived 
from  the  waste  of  the  land.  In  the  deeper  sea  the  cover- 
ing is  a  fine-textured  material  of  animal  origin  called 
ooze.  It  is  composed  of  the  shells  of  minute  animals  that 
live  near  the  surface.  The  most  abundant  shell  is  that  of 
a  minute  animal  called  the  globigerina,  hence  the  deposit  is 
often  called  the  globigerina  ooze. 

At  a  depth  of  about  3000  fathoms  (18,000  feet)  these 
shells  disappear  and  a  reddish  clay  appears.  This  clay  is 
believed  to  be  due  to  meteoric  and  volcanic  dust  and  to 
the  insoluble  parts  that  remain  after  the  calcareous  (lime- 


CBINOID. 

An  animal  now  found  only  at  considerable 
depths  in  the  ocean. 


WAVES 


277 


like)  material  of  the  minute  shells  has  been  dissolved  in 

sinking  through  the  deep  water.     No  layers  of  this  kind 

have  ever  been  found  on 

the  land,  and  this  is  one  of 

the   reasons  for   believing 

that  the  depths  of  the  sea 

have  never  been  elevated 

into    dry    land,    but    that 

what    is    now  deep   ocean 

has    throughout    all    time 

been  deep  ocean. 

131,  Waves.  —  Experiment 
124.  —  Take  a  long  flexible 
rubber  band  or  tube  and  having 
fastened  one  end,  stretch  it  GLOBIGBRINA. 

somewhat.      Now   strike  down 

on  it  near  one  end  with*  a  small  stick.  A  wavelike  motion 
will  be  seen  to  travel  from  end  to  end  of  the  band.  It  is  evident 
that  the  particles  of  rubber  do  not  enter  into  the  lateral  move- 
ment, but  that  they  simply  move  up  and  down,  whereas  the  wave 
movement  proceeds  along  the  band.  A  piece  of  paper  folded  and 
placed  lightly  upon  the  band  will  move  up  and  down  but  not  along 
the  band.  Thus  wave  motion  does  not  necessitate  lateral  movement 
of  the  particles  taking  part  in  the  wave. 

When  the  wind  blows  over  water,  it  throws  the  surface 
into  motion  and  produces  waves.  The  highest  part  of  the 
wave  is  called  the  crest  and  the  lowest  part  the  trough. 
Trough  and  crest  move  along  rapidly  over  the  surface  of 
the  water.  The  particles  of  the  water  themselves,  how- 
ever, move  somewhat  like  those  in  the  rubber  band.  That 
the  water  itself  does  not  move  with  the  wave  can  be  seen 
when  a  floating  bottle  is  observed.  It  moves  up  and  down 
but  does  not  move  forward.  If  the  water  moved  along 
with  the  waves,  it  would  be  next  to  impossible  to  pro- 
pel a  boat  against  the  direction  of  the  wave  movement. 


278 


FIRST   TEAR   SCIENCE 


That  it  is  possible  to  generate  wave  movement  with- 
out the  particles  themselves  moving  along  with  the  wave 
is  seen  when -a  field  of  grain  is  bending -before  a  gentle 
wind.  The  troughs  and  crests  move  one  after  the  other 
across  the  field  but  the  heads  of  grain  simply  vibrate  back 
and  forth.  The  crest  of  a  water  wave,  however,  is  often 
blown  forward  by  the  wind  and  thus  a  drift  in  the  direc- 
tion of  the  wind  is  established  at  the  surface. 


OCEAN  WAVES. 

When  great  waves  are  raised  by  the  wind  at  sea,  there 
is  danger  that  the  mighty  crests  may  be  blown  forward 
and  engulf  a  ship.  To  calm  the  waves  ships  sometimes 
pour  "oil  on  the  troubled  waters."  The  oil  spreads 
out  in  a  thin  film  over  the  water  and  forms  a  "  slick  " 
which  prevents  the  wind  from  getting  sufficient  hold  upon 
the  water  to  topple  over  the  crests,  and  thus  the  danger 
of  being  swamped  is  averted.  It  has  been  found  that  oil 
will  spread  out  even  in  the  direction  of  the  severest  wind. 

Although  sometimes  waves  are  spoken  of  as  "  mountain 


TEMPERATURE  OF  OCEAN   WATERS  279 

high,"  it  rarely  happens  that  the  height  from  trough  to 
crest  is  over  50  ft.  The  length  of  these  great  ocean  waves, 
or  the  distance  from  crest  to  crest  or  from  trough  to  trough 
varies  from  300  to  1500  ft.  or  more.  The  velocity  is 
sometimes  as  great  as  60  miles  per  hour,  but  usually  not 
more  than  half  of  this.  The  movement  of  the  waves  stirs 
up  the  water  and  enables  it  to  absorb  the  air  which  is  so 
necessary  for  the  existence  of  water  animals. 

Earthquakes  occurring  under  the  sea  sometimes  gen- 
erate great  waves  which  sweep  in  over  the  land  destroying 
coast  towns  and  shipping.  These  waves  sometimes  rise 
to  a  height  of  even  a  hundred  feet  above  sea  level.  Ships 
have  been  carried  by  them  a  long  distance  inland  and  left 
high  and  dry.  These  waves,  wrongly  called  tidal  waves, 
have  no  connection  with  the  wind. 

132.  Temperature  of  Ocean  Waters. — Experiment  126. — Fill 
a  flask  of  about  500  cc.  with  water.  Press  into  the  mouth  of  the 
flask  a  cork  through  which  a  glass  tube  about  30  cm.  long  extends. 
The  tube  should  be  open  at  both  ends  and  should  not  extend  into  the 
flask  below  the  bottom'  of  the  cork.  When  the  cork  is  pressed  in,  the 
water  will  be  forced  up  into  the  tube  for  several  centimeters.  See 
that  the  cork  is  tight  and  that  there  are  no  bubbles  of  air  in  the  flask 
or  tube. 

Now  place  the  flask  for  fifteen  or  twenty  minutes  in  a  mixture  of 
ice  and  water  and  carefully  mark  with  a  rubber  band  the  point  at 
which  the  water  in  the  tube  comes  to  rest.  Take  the  flask  out  of  the 
freezing  mixture  and  notice  immediately  whether  the  water  in  the 
tube  rises  or  falls.  Continue  for  five  or  ten  minutes  to  notice 
the  action  of  the  water  in  the  tube.  The  volume  of  the  water  is  not 
the  least  when  it  is  at  the  temperature  of  melting  ice,  32°  F.,  but 
when  it  is  a  little  above  this  temperature. 

Unlike  fresh  water,  which  is  densest  at  a  little  above 
freezing,  sea  water  continues  to  decrease  in  volume  and 
grows  denser  as  it  is  cooled,  until  it  reaches  its  freezing 
point  at  28°  F.  Hence  the  cold  water  near  the  poles 


THE  BEST-KNOWN  OCEAN  CURRENTS  281 

gradually  sinks  and  creeps  under  the  warmer  water  of 
lower  latitudes  maintaining  a  temperature  of  32°  to  35° 
on  the  bottom,  even  at  the  equator.  This  steady  creep 
of  cooled  surface  water  along  the  bottom  supplies  the 
animals  of  the  deep  ocean  floor  with  the  air  which  they 
must  have.  Without  it  the  water  at  great  depths  would 
have  its  air  exhausted  and  all  life  would  be  destroyed. 

At  the  surface  of  the  ocean  the  temperature  of  the  water 
varies  in  a  general  way  with  the  latitude ;  it  is  over 
80°  at  the  tropics  and  about  the  freezing  point  at  the 
poles.  Near  the  poles  and  near  the  equator  there  is  very 
little  variation  in  the  temperature  of  the  surface  water 
during  the  year,  but  in  the  intermediate  latitudes  the 
annual  variation  is  considerable.  Below  the  surface  the 
effect  of  solar  heat  rapidly  diminishes  and  at  a  depth  of 
300  ft.  it  is  probable  that  the  annual  variation  in  tempera- 
ture is  nowhere  more  than  2°  F.  Below  600  ft.  there  is 
probably  no  annual  change  in  temperature. 

On  the  surface  the  daily  average  range  of  temperature 
is  not  more  than  1°  F.  and  the  annual  range  does  not 
exceed  fifteen  degrees,  except  where  the  same  surface 
is  washed  at  different  seasons  by  currents  of  different 
character,  and  near  the  shore,  where  the  heat  of  the  land 
affects  it.  This  contrast  in  temperature  conditions  be- 
tween the  ocean  and  the  land  is  most  marked.  The  life 
conditions  in  one  are  uniform  and  unvaried  while  in  the 
other  they  are  most  changeable  and  are  subject  to  ex- 
tremes of  temperature.  •  That  is  why  the  land  animals 
must  be  much  more  highly  organized  than  those  of  the 
sea  in  order  to  survive  these  changeable  conditions. 

133.  The  Best-known  Ocean  Currents.  —  The  ocean  is  a 
region  of  never-ceasing  motion.  At  considerable  depths 
its  motion  is  very  slow,  but  near  the  surface,  where  the 
prevailing  winds  can  affect  it,  the  movement  is  consider- 


282  FIBST  YEAR   SCIENCE 

'      '      *        .  4** 

able.  Circulating  around  each  ocean  there  is  a  contin- 
uous drift  of  surface  water  extending  to  a  depth  of  from 
300  to  600  feet  and  varying  in  rate  from  a  few  miles  up 
to  fifty  or  more  miles  a  day.  In  fact  these  rotating 
currents  are  the  chief  natural  basis  for  the  division  of  the 
oceanic  area  into  six  oceans,  as  our  geographies  generally 
divide  them. 

These  currents  circulate  in  the  northern  hemisphere  in 
the  direction  in  which  the  hands  of  a  watch  move  and 
in  the  southern  hemisphere  in  the  opposite  direction.  In 
the  centers  of  these  rotating  areas  the  water  is  nearly 
motionless  and  here  are  often  found  great  masses  of  float- 
ing seaweed  filled  with  a  great  variety  of  small  animals. 
These  accumulations  of  seaweed  are  called  sargasso  seas 
(page  249). 

That  these  surface  drifts  have  a  definite  direction  of 
movement  is  indicated  by  observations  made  on  the 
courses  taken  by  a  great  number  of  wrecks.  The  di- 
rection of  these  movements  has  also  been  determined  by 
throwing  from  ships  in  different  parts  of  the  ocean  thou- 
sands of  bottles  in  which  had  been  placed  the  date  and  a 
record  of  the  latitude  and  longitude  of  the  ship.  The 
places  where  the  bottles  came  ashore  showed  the  direction 
of  the  currents. 

If  the  movement  of  the  water  is  slow,  ten  or  fifteen 
miles  a  day,  it  is  called  a  drift;  if  faster,  a  current.  The 
principal  currents  have  been  given  names  and  have  been 
most  carefully  charted.  The  warm  current  that  flows 
northeastward  off  the  southeast  coast  of  North  America  is 
called  the  Grulf  Stream.  That  off  the  east  shore  of  Asia, 
which  also  flows  northeast,  is  called  the  Kuro  Siwo  or 
Japan  Current.  The  cold  current  off  the  east  coast  of 
Labrador  flowing  southeast  is  called  the  Labrador  Current ; 
and  the  cold  current  which  flows  northward  off  the  west 


EFFECTS   OF  OCEAN  CURRENTS 


283 


coast  of  South  America  is  called  the  Humboldt  Current. 
Other  names  are  given  to  different  parts  of  the  ocean  move- 
ment, but  those  mentioned  here  are  the  most  important. 

Where  the  ocean  currents  are  unimpeded  by  the  land, 
they  flow  in  the  direction  of  the  prevailing  winds.  It 
has  been  found  that  the  currents  change  their  directions 
with  a  change  in  the  direction  of  the  prevailing  wind, 
such  as  occurs  in  the  Indian  Ocean  when  the  heat  equator 
is  farthest  north  of  the  earth's  equator.  It  appears  that 
ocean  currents  are  primarily  a  result  of  the  wind  circulation. 

134.  Effects  of  Ocean  Currents.  —  A  knowledge  of  ocean 
currents  is  of  importance  to  mariners,  as  the  course  and 
speed  of  a  vessel  may  be  considerably  affected  by  them. 
They  also  greatly  affect  the  conditions  of  animal  life  in 


CORAL  FORMATIONS  IN  THE  BERMUDAS. 

different  parts  of  the   sea.     Not  only  do  these  currents 
bring  food  to  animals  which  have  not  the  power  of  motion 


284  FIRST  YEAR   SCIENCE 

'  *  '  f* 

but  they  determine  the  area  in  which  certain  animals  may 

live. 

The  Bermudas,  32°  north  of  the  equator,  are  coral  reef 
formations,  while  the  Galapagos,  almost  on  the  equator, 
are  surrounded  by  too  cold  water  to  have  any  such  reefs. 
At  68°  north,  near  the  Lofoten  Islands,  are  the  great  cod 
fisheries  of  Europe.  On  the  western  side  of  the  Atlantic 
these  fisheries  are  on  the  Grand  Banks,  latitude  45° 
north.  Many  other  similar  illustrations  of  the  effects  of 
these  currents  on  the  distribution  of  animal  life  might  be 
cited. 

The  temperature  of  winds  blowing  from  the  sea  is 
modified  by  these  currents  and  greatly  affects  the  habita- 
bility  of  the  earth  for  man.  Hammerfest  at  71°  north  is 
a  flourishing  seaport,  but  there  are  no  important  settle- 
ments above  50°  on  the  western  side  of  the  Atlantic. 
Alaska,  the  prevailing  winds  of  which  are  warmed  by 
blowing  over  the  warm  ocean,  is  a  region  which  promises 
much  for  human  habitation,  while  the  region  on  the  op- 
posite side  of  the  Pacific  must  remain  almost  destitute  of 
human  inhabitants.  It  should  be  noted  that  the  effect  of 
the  warm  ocean  waters  would  be  slight,  except  along  the 
coast,  were  it  not  for  the  air  movements. 

135.  Tides.  —  Probably  the  first  thing  that  impresses  us 
on  visiting  the  seashore  is  the  regular  rising  and  falling 
of  the  water  each  day.  These  movements  of  the  water 
are  called  tides.  If  we  observe  the  tides  for  a  few  days, 
we  find  that  there  are  two  high  and  two  low  tides  each 
day.  As  the  tidal  current  comes  in  from  the  open  ocean 
and  the  water  rises,  it  is  called  flood  tide,  and  as  it  runs  out 
or  falls,  ebb  tide.  When  the  tides  change  from  flood  to 
ebb  or  ebb  to  flood,  there  is  a  brief  period  of  "  slack  water." 

If  we  observe  closely,  we  shall  see  that  the  correspond- 
ing tides  are  nearly  an  hour  later  each  day  than  they  were 


TIDES 


285 


HIGH  TIDE  IN  THE  BAY  OF  FUNDY. 


the  day  before,  and  that  the  time  required  for  the  comple- 
tion of  two  higjfand  two  low  tides  is  nearly  25  hours.  Con- 
tinued observation  will 
show,  as  Julius  Caesar 
stated  many  centuries 
ago,  that  there  is  ap- 
parently a  relation  be- 
tween the  phases  of  the 
moon  and  the  height  of 
the  tides.  The  greatest 
rise  and  fall  of  the  water 
will  be  found  to  occur 
about  the  time  of  full 
and  new  moon. 

The   amount   of    rise 
and  fall  of  the  tides  is 
not  the  same  in  different  places.     Upon  shores  of  oceanic 
islands  the  difference  between  high  and  low  water,   or 

the  range,  as  it  is  called, 
is  not  more  than  two  or 
three  feet.  In  funnel- 
shaped  bays  where  the 
tidal  current  is  com- 
pressed as  it  moves  in 
toward  the  bay  head, 
the  range  is  very  much 
greater.  In  the  Bay 
of  Fundy  the  range  is 
sometimes  as  great  as 
seventy  feet. 

Sometimes  these  com- 
pressed tidal  currents 
are  formed  at  the  mouths  of  rivers  and  move  up  the 
rivers  like  a  wall  of  surf  several  feet  in  height,  en- 


Low  TIDE  AT  THE  SAME  PLACE. 


286  FIRST  YEAR   SCIENCE 

' '  '  ** 

dangering  all  vessels  which  are  not  securely  moored. 
Such  tidal  surfs  are  called  bores  and  are  found  in  the 
Seine,  Amazon  and  other  rivers.  • 

The  tidal  current  as  it  sweeps  between  islands  often 
forms  eddies  and  whirlpools  which  make  navigation  very 


AN  ATOLL  IN  THE  MID-PACIFIC. 

dangerous.  An  example  of  this  is  found  at  Hell  Gate, 
N.  Y.,  and  at  the  famous  Maelstrom  off  the  coast  of  Nor- 
way. On  the  other  hand  in  flat  countries  where  the  rivers 
are  shallow,  ports  which  could  not  otherwise  be  reached 
are  made  accessible  to  ships  of  considerable  burden  at  the 
time  of  high  tide.  At  these  places  the  time  of  leaving  or 
making  port  changes  each  day  with  the  time  of  high  tide. 
A  striking  example  of  this  is  the  port  of  Antwerp. 


TIDES 


287 


The  tidal  currents  are  also  continually  changing  the 
water  in  bays  and  harbors  and  thus  keeping  them  from 
becoming  stagnant  and  foul.  They  also  bring  food  to 
many  forms  of  shore  life  which  have  but  little  or  no  power 
of  movement,  such  as  clams  and  other  shellfish,  and  by 
exposing  some  of  these  at  the  ebb  give  man  a  chance  to 
acquire  them  readily  for  food.  ' 


THE  VATERLAND. 
One  of  the  largest  vessels  afloat. 

It  has  been  found  that  the  position  of  the  sun,  as  well  as 
that  of  the  moon,  affects  the  height  of  the  tide.  If  the 
earth,  moon  and  sun  lie  in  nearly  the  same  line,  the  tidal 
range  is  greatest.  This  is  called  spring  tide.  When  the 
sun  and  moon  act  at  right  angles  upon  the  earth,  the  tidal 
range  is  least  and  this  is  called  neap  tide.  The  tidal  undu- 
lations have  been  proved  by  astronomers  to  be  due  to  the 
rotation  of  the  earth  and  the  gravitational  attraction  of 


288 


FIRST   YEAR   SCIENCE 


the  sun  and  moon  upon  its  water  envelop.  The  moon  is 
much  the  more  effective  because  it  is  nearer. 

In  the  open  sea  the  rise  and  the  fall  of'  the  tides  are  of 
equal  duration  but  at  the  head  of  bays  the  tide  rises  more 
rapidly  than  it  falls  so  that  low  tide  does  not  occur  mid- 
way between  two  successive  high  tides. 

136.  Corals  and  Coral  Islands.  —  In  warm,  clear,  shallow 
areas  of  the  sea  are  found  small  animals  called  corals. 


PANAMA 


An  example  of  man's  domination  over  nature. 


Great  colonies  of  these  are  able  by  united  action  to 
build  barriers  capable  of  withstanding  the  waves  and  of 
raising  submarine  lands  into  islands.  These  reef-building 
corals  cannot  live  at  a  greater  depth  than  20  fathoms  (120 
feet),  or  where  the  mean  temperature  is  lower  than  68°  F., 
or  where  the  discharge  of  rivers  makes  the  water  fresh  or 
muddy.  As  they  are  fixed  animals  and  must  get  their 
food  from  the  surrounding  water,  they  flourish  best  where 


MAN  AND   THE  OCEAN 


289 


the  warm  currents  flow  past  continually,  bringing  a  fresh 
supply  of  food.  In*  tropical  seas  many  islands  are  fringed 
by  reefs  built  by  these  animals. 

In  the  tropical  Pacific  circular  coral  reefs  are  found 
nearly  inclosing  large  shallow  lagoons.  Soundings  out- 
side of  these  reefs  show  that  the  sea  rapidly  sinks  to  great 
depths.  Islands  of  this  kind  are  called  atolls.  How  these 
atolls  were  formed  is  still  an  open  question.  As  reef- 


CANAL. 


Two  great  oceans  artificially  united. 


building  corals  cannot  live  below  20  fathoms,  it  is  evident 
that  corals  could  not  have  built  up  the  reefs  from  the  bot- 
tom of  the  deep  sea. 

137.  Man  and  the  Ocean. — At  first  thought  it  would 
seem  better  for  the  life  of  the  world  if  the  proportion 
of  land  and  water  were  reversed.  Yet  when  we  consider 
that  almost  barren  wastes  constitute  many  continental 
interiors  and  that  plenty  of  rainfall  is  necessary  to  make 


290  FIRST   YEAR   SCIENCE 

'    *  v* 

land  habitable,  the  utility  of  the  great  water  surfaces 
becomes  apparent.  From  the  evaporation  of  the  ocean 
surface  comes  nearly  all  the  water  which  supplies  man, 
land  animals  and  plants. 

It  is  not  only  true  that  all  streams  eventually  run  to  the 
sea  but  it  is  also  true  that  all  their  water  comes  from 
the  sea.  Other  things  being  equal,  the  smaller  the 
surface  for  evaporation  the  less  the  water  supplied  to 
the  land.  Besides  supplying  the  land  with  water,  the 
ocean  has  a  great  effect  on  its  climate.  The  animals  of 
the  sea  also  furnish  food  for  thousands.  A  large  part 
of  the  earth's  population  is  now,  and  always  has  been, 
located  not  far  from  the  shore  of  the  ocean. 

In  early  times  before  the  advent  of  railways  almost  all 
commerce  was  carried  on  over  the  sea.  Even  now  this  is 
the  cheaper  way  of  transportation.  Modern  methods  of 
conveyance  have  enabled  man  to  live  with  comfort  at  a 
considerable  distance  from  the  ocean,  but  the  dry  interiors 
of  continents  still  remain  sparsely  inhabited.  All  com- 
mercial nations  must  have  an  outlet  to  the  sea  and  to 
obtain  it  much  blood  and  treasure  have  often  been  spent. 
Man  for  his  commerce  has  even  broken  through  the  bar- 
riers by  which  nature  has  separated  seas  and  oceans,  as  in 
the  case  of  the  Suez  and  Panama  canals. 

Summary.  —  The  sea  occupies  nearly  three  quarters  of 
the  area  of  the  globe.  It  is  usually  spoken  of  as  divided 
into  oceans,  the  Atlantic,  Pacific,  Indian,  Arctic  and  Ant- 
arctic. Although  some  parts  of  the  ocean  are  nearly  six 
miles  deep,  the  most  interesting  and  most  extensively  in- 
habited part  of  it  is  that  above  the  continental  shelf.  This 
shelf  is  the  gradual  slope  from  the  edge  of  the  different 
continents  to  a  depth  of  about  six  hundred  feet.  Beyond 
this  the  descent  becomes  rapid. 


SUMMARY  291 

On  the  surface  of  the  sea  are  waves  varying  in  height 
from  a  few  inches  to  fifty  feet.  These  stir  up  the  water 
and  enable  it  to  absorb  more  air,  which  is  so  necessary  to 
the  living  things  in  the  sea.  Not  only  is  the  surface  of 
the  sea  constantly  in  motion,  but  there  are  also  great  cur- 
rents, such  as  the  Gulf  Stream,  which  carry  the  water  from 
one  latitude  to  another.  These  currents  are  caused  almost 
entirely  by  the  winds. 

The  tides  are  due  primarily  to  the  action  upon  each 
other  of  the  earth,  moon  and  sun.  The  range  of  tides 
varies  from  two  or  three  feet  on  oceanic  islands  to  about 
seventy  feet  at  some  places  in  the  Bay  of  Fundy.  The 
tides  help  drainage  and  assist  vessels  over  bars  that  would 
otherwise  be  impassable. 

QUESTIONS 

What  portion  of  the  earth's  surface  is  sea  ?  Into  what  divisions  is 
the  sea  usually  divided  ? 

What  is  the  continental  shelf?  Why  is  it  of  especial  interest  to 
man  ? 

Of  what  is  the  sea  water  composed  ?  How  does  its  composition 
affect  animals  ? 

If  you  were  able  to  take  a  trip  from  the  nearest  beach  over  the 
ocean  bed  to  another  continent,  describe  what  you  would  probably 
find  along  the  way. 

What  are  waves?     What  causes  them ?  o 

What  is  the  temperature  of -the  ocean  water  in  different  parts  of 
its  surface  and  at  different  depths? 

Describe  the  best  known  ocean  currents.  What  is  the  cause  of 
these  ?  Why  is  a  knowledge  of  ocean  currents  important  to  mariners 
and  also  to  those  who  would  explain  the  climates  of  different  places  ? 

What  are  tides?     What  causes  them?     What  are  their  effects? 

How  are  coral  reefs  formed  ?     What  are  atolls  ? 

In  what  ways  is  the  ocean  useful  to  man  ? 


CHAPTER   IX 

COAST  LINES 

138.  Coast  Lines.  —  On  examining  a  map  or  chart  of  an 
extended  coast  one  cannot  fail  to  be  impressed  with  its 
irregularity.  Although  it  may  extend  for  long  distances 


POSITANO. 

A  precipitous  and  densely  populated  coast. 

in  an  almost  unbroken  straight  line,  as  along  the  south- 
eastern part  of  the  Bay  of  Biscay,  yet  if  we  follow  even 
this  coast  far  enough  in  either  direction,  it  becomes  mark- 
edly irregular.  Islands  composed  of  the  same  material  as 

292 


COAST  LINES  293 

the  coast  itself  are  often  found  near,  separated  from  it 
only  by  shallow  arms  of  the  sea.  These  are  evidently 
a  part  of  the  adjacent  mainland  with  a  submerged  portion 
between. 

Sometimes  in  warm  latitudes  where  conditions  are  suit- 
able, the  coast  is  bordered  for  a  long  distance  by  coral 
reefs.  The  northeast  coast  of  Australia  affords  a  marked 


NORTH  CAPE. 
A  famous  promontory  which  defies  the  waves  of  the  North  Atlantic. 

example.  Here  a  barrier  reef  extends  for  a  thousand 
miles  along  the  coast,  protecting  it  and  leaving  a  smooth 
water  channel  10  to  30  miles  broad  for  coastwise  naviga- 
tion. 

A  coast  in  warm  regions  may  also  be  protected  by 
the  growth  of  dense  thickets  of  mangroves.  This  tree 
grows  in  shallow  water  and  sends  down  from  its  branches 
roots  upon  which  crabs  and  oysters  live  and  among  which 


294 


FIRST    YEAR   SCIENCE 


mud  and  debris  accumulate/  Thus  low  shores  are  slowly 
being  built  out  into  the  sea.  Shore  borders  of  this  kind 
are  found  extending  many  miles  along,  the  coasts  of 
southern  Florida  and  Texas  and  in  many  other  places. 

In  extreme  northern  and  southern  latitudes  the  coast 
may  be  fringed  for  long  distances  with  ice.  In  middle 
latitudes,  however,  the  coast  is  generally  composed  of  rock, 


FINGAL'S  CAVE. 

sand  or-  mud  and  is  sometimes  protected  by  a  thick  sea- 
weed mantle.  Here,  besides  the  usual  forces  of  erosion 
and  deposition  found  active  on  the  land,  are  the  forces  of 
the  waves  and  currents. 

139.  Wave  Cutting.  —  Wherever  the  waves  strike  on  an 
unprotected  shore,  they  wear  it  away.  The  rapidity  of 
the  cutting  and  the  forms  carved  depend  upon  the 
strength  of  the  waves  and  the  kind  of  shore.  Wherever 
there  is  a  point  of  weakness  along  the  shore,  there  the 
waves  cut  back  more  rapidly.  The  harder  parts  stand 


WAVE  CUTTING 


295 


out  sharply  as  points  and  promontories.  In  some  cases 
the  waves  cut  back  so  rapidly  on  lofty  coasts  that  high 
cliffs  are  formed. 

If  the  material  of  the  coast  does  not  readily  break  off 
when  undercut  by  the  waves,  a  sea  cave  may  be  formed. 
Such  is  the  well-known  Fingal's  cave  on  an  island  off  the 
coast  of  Scotland  where  the  structure  of  one  of  the  igne- 
ous rock  layers  allows  the  waves  to  quarry  it  compara- 
tively easily.  Spouting  holes  and  caves  are  usually  due 
to  an  easily  eroded  place  in  the  shore  where  the  waves 
are  able  to  cut  back  a  somewhat  horizontal  tunnel  and  by 
their  impact  upon  the 
end  of  the  excavation 
form  an  opening  to  the 
surface  through  which 
spray  is  ejected.  The 
hole  may,  be  at  some 
little  distance  from  the 
shore. ' 

Since  waves  have  the 
power  of  cutting  only 
to  a  small  depth,  it  may 

happen  that  an  exposed  rocky  coast  will  have  a  bench 
cut  along  it,  under  the  surface,  backed  by  a  sea  cliff 
against  which  the  waves  are  still  cutting.  If  such  a 
coast  becomes  elevated,  the  rock  bench  will  appear  with  a 
cliff  terminating  it  on  the  landward  side.  If  a  coast  stays 
at  the  same  elevation  long  enough,  or  if  its  material  is 
easily  eroded,  large  areas  of  what  was  formerly  dry  land 
may  be  cut  away  and  brought  under  the  sea. 

In  1399  Henry  of  Lancaster,  afterward  Henry  IV  of 
England,  returned  from  his  exile  and  landed  at  Ravenspur, 
an  important  town  in  Yorkshire,  to  begin  his  fight  for  the 
crown.  A  person  disembarking  at  the  same  place  to-day 


296 


FIRST   YEAR   SCIENCE 


would  be  so  far  from  shore  that  he  would  need  to  be  a 
sturdy  swimmer  to  reach  the  beach.  The  entire  area 
of  the  ancient  town  has  been  cut  away  byHhe  waves  and 
now  lies  under  the  sea.  This  is  an  example  of  what  has 
occurred  in  many  sea  coast  regions. 

140.   Beaches   and  Bars. —  Unless  the  material   pillaged 
from  the  land  by  the  waves  falls  into  too  deep  water,  it  is 

buffeted  about  by  them 
and  broken  and  worn 
into  small  pieces. 
These  are  then  borne 
along  by  the  shore  cur- 
rents until  they  find 
lodgment  in  some  pro- 
tected place  where  they 
can  accumulate.  When 
sufficient  material  has 
been  accumulated,  the 
storm  waves  and  the 
wind  sweep  some  of  it 
above  sea  level  and 
fringe  the  water's  edge 
with  a  border  of  water- 
worn  sand  and  pebbles. 
These  accumulations  of 
shore  drift  are  called 
beaches. 

The  incoming  waves 
are  constantly  sweep- 
ing in  material  from  the  shallow  bottom  against  which 
they  strike,  and  the  returning  undertow  bears  its  load 
seaward.  Except  in  time  of  great  storms  the  accumu- 
lation of  material  along  a  beach  is  at  least  equal  to 
the  wearing  away. 


A   LAKE    BEACH    FORMED    BY    STREAM 

AND  WAVE  ACTION. 

A  year  after  this  picture  was  taken  a 

landslide  formed  a  wave  which  swept 

away  the  entire  beach  and  village. 


WAVE  CUTTING  297 

The  currents  moving  the  loose  material  with  them  some- 
times form  it  into  bars  which  inclose  or  tie  islands  to  the 
mainland  or  extend  into  the  sea  free  ends,  forming  what 
are  called  spits.  A  famous  example  of  a  land-tied  island 


NAHANT,  MASSACHUSETTS. 
A  land-tied  island. 


is  that  of  the  great  English  fortress  at  Gibraltar ;  although 
now  a  promontory,  it  was  once  an  island  detached  from 
the  coast  of  Spain.  Shifting  sand  bars,  especially  if  cov- 
ered with  water,  are  exceedingly  dangerous  to  vessels,  and 
coasts  where  these  are  abundant  need  especial  protection 


298 


FIRST   YEAR   SCIENCE 


by  lighthouses  and  life-saving  stations.  The  greatest 
Mediterranean  port  of  France  during  the  thirteenth  cen- 
tury, Aigues-Mortes,  has  been  closed  in  by  sand  bars  so 
that  there  is  no  longer  access  to  the  sea  and  only  the  relics 
of  the  former  great  city  now  exist.  Thus  have  the  mov- 
ing sea  sands  overthrown  the  plans  of  men. 


A  SAND  SPIT. 
Formed  by  the  waves  and  currents. 

141.  Final  Effect  of  Wave  and  Current  Action.  —  Whether 
the  coast  is  shallow  so  that  the  storm  waves  spend  their  force 
off  shore,  or  deep  so  that  they  batter  the  shore  with  their 
full  strength,  the  tendency  is  to  straighten  the  coast  line. 
In  the  former  case  sand  reefs  with  gently  flowing  outlines 
are  built,  and  in  the  latter  case  the  headlands  are  cut  away 
by  the  waves  and  the  material  moved  along  by  the  coast 
currents  to  fill  the  protected  bays  and  coves.  As  aerial 
erosion  is  constantly  tending  to  smooth  off  the  irregulari- 


INSTABILITY  OF  SEA    COASTS 


299 


ties  of  the  land  surface,  so  the  waves  and  currents  of  the 
ocean  are  constantly  straightening  out  the  water  margins. 
Uniformity  seems  to  be  the  goal  for  the  erosive  forces. 
But  when  the  results  of  surface  erosion  are  brought  to  the 
sea  by  the  rivers,  deltas  are  formed  which  interfere  with  the 
straightening  of  the  coast.  If  the  material  brought  by  the 


A  BEACH  AT  CATALINA  ISLAND. 
Notice  how  the  water  is  smoothing  out  the  irregularities  of  the  land. 

rivers  is  sufficient,  a  delta  is  built  out  into  the  sea  in  spite 
of  the  action  of  the  waves  and  currents  and  the  coast  line 
becomes  increasingly  irregular.  Lake  shores  are  acted 
upon  in  a  similar  way  and  with  similar  results,  only  the 
forces  here  are  less  powerful  than  those  that  act  upon  the 
sea  coasts. 

142.   Instability  of  Sea  Coasts.  —  It  often  happens  that  in 
making  excavations  at  a  considerable  distance  from  the 


300 


FIRST   YEAR   SCIENCE 


sea,  shells  are  dug  up  very  similar  to  those  now  found  on 
the  shore.  Some  inland  strips  of  land  are  found  com- 
posed of  sand  and  pebbles  like  a  beach  and  having  the  beach 
slope.  Sometimes  tree  trunks  standing  with  their  roots 
in  the  ground  just  as  they  do  on  the  dry  land  are  seen  at  a 
considerable  depth  in  the  sea.  It  can  be  proved  that  an 


INLAND  SEA  CAVE  AND  BEACH. 
This  coast  has  been  recently  elevated. 

old  temple  near  Naples,  Italy,  has  stood  above  and  then 
in  the  sea  more  than  once  since  it  was  built. 

Facts  like  these  show  that  the  sea  coast  is  not  stable, 
but  subject  to  upward  and  downward  movements,  some  of 
which  are  slight  and  some  great.  If  the  land  near  the  sea 
rises,  the  coast  line  is  moved  into  the  area  which  was  for- 
merly covered  by  the  water  and  if  the  land  sinks,  a  new  coast 
line  is  formed  where  before  the  hills  and  valleys  of  the 
land  appeared.  Changes  of  this  kind  have  a  marked  effect 


ELEVATED   COAST 


301 


upon  the  outline  of  the  coast  and  upon  the  industries  of 
its  future  inhabitants.  The  coastal  plain  which  borders  a 
large  part  of  our  Atlantic  coast  shows  the  results  of  an 
upward  movement.  The  fiorded  coast  of  Alaska  affords 
an  example  of  a  downward  movement. 


TEMPLE  OF  JUPITER  NEAR  NAPLES. 

Although  it  can  be  proved   that   this  coast  has  been  elevated  and  de- 
pressed several  times,  so  gradual  has  been  the  movement  that  the  pillars 
have  not  been  overturned. 

143.  Elevated  Coast.  —  Experiment  126.  —  Tack  enough  sheet 
lead  to  a  very  rough  board  so  that  it  will  remain  submerged  when 
placed  in  water.  Place  the  board  in  a  shallow  dish  of  water,  lead 
side  down.  Taking  the  board  by  one  edge,  gradually  lift  this  edge 
above  the  water  surface.  What  kind  of  a  line  does  the  water  form 
where  it  meets  the  board?  In  what  way  would  this  line  be  changed 
if  the  board  were  smoother?  If  it  were  rougher?  If  the  edge  of  the 
board  is  lifted  higher,  does  the  position  of  the  water  line  change? 
Does  its  form  materially  alter  ? 


302  FIRST   YEAR   SCIENCE 

The  main  characteristics  of  a  coast  which  has  been  ele- 
vated, that  is,  of  one  in  which  the  shore  line  has  moved  sea- 
ward, will  readily  suggest  themselves  to  any  one  who 
considers  what  has  taken  place.  Soundings  show  that  the 
continental  shelf  has  a  comparatively  smooth  surface. 
Thus  the  water  will  meet  the  land  in  an  almost  straight 
line  and  the  deepening  of  the  water  off  shore  will  be  grad- 
ual. The  material  forming  the  shore  both  below  and 
above  the  water  line  will  be  easily  eroded,  since  it  has 
been  recently  deposited  and  has  not  had  time  to  consolidate. 


SAND  DUNES  FORMED  UPON  A  SAND  BAR. 

Waves  rolling  in  upon  the  shore  will  strike  the  bot- 
tom at  a  considerable  distance  off  shore.  Thus  the  water 
rapidly  loses  its  velocity  and  its  power  to  carry  eroded 
material  shoreward,  so  it  builds  at  a  distance  from  the 
shore  a  sand  reef  inclosing  a  lagoon.  The  currents  caused 
by  the  prevailing  winds  and  the  tide  flowing  along  the  out- 
side of  this  barrier  give  it  for  long  distances  a  smooth 
outline,  sometimes  almost  straight  and  sometimes  gently 
curving.  Dunes  are  formed  upon  these  bars.  In  time 


ELEVATED  COAST  303 

landward-blown  sand,  together  with  the  silt  brought  by  the 
streams  from  the  mainland,  may  fill  up  the  lagoon. 

The  filling  of  these  lagoons,  both  naturally  and  artificially, 
has  considerably  increased  the  habitable  land  of  the  earth. 
The  inclosed  waterway  back  of  the  sand  reefs  has  in  some 
places  rendered  coastwise  traffic  safe  and  easy.  It  is  pro- 
posed artificially  to  extend  and  develop  certain  of  these 
inclosed  water  areas  along  the  eastern  coast  of  the  United 
States  so  as  to  form  a  protected  waterway  from  New 
England  to  the  southern  ports.  At  present  the  low,  almost 
featureless  shore  of  this  region,  with  its  shifting  sand  bars 
and  capes,  makes  coastwise  navigation  dangerous,  although 
it  is  protected  by  many  lighthouses  and  life-saving  stations. 

The  sand  reefs  along  the  southern  Atlantic  and  Gulf 
coasts  have  in  some  places  attained  sufficient  width  and 
height  for  considerable  settlements.  The  tidal  inlet,  the 
sea-beach  resort,  and  the  commercial  city  with  reef-pro- 
tected harbor  are  natural  results  of  receding  shore  lines. 
In  time  the  waves,  by  their  own  erosive  action,  will  deepen 
the  bottom  off  shore  from  the  reef  enough  to  enable  them 
to  attack  its  front.  Thus  they  will  drive  it  back  over  the 
inclosed  lagoon,  destroying  their  own  work  and  attacking 
the  shore,  which  for  a  time  they  had  shielded  against  their 
own  rapacity. 

Where  the  range  of  tide  is  considerable,  the  reefs  are 
frequently  broken  by  inlets.  Through  these  the  water 
of  the  mainland  streams  finds  access  to  the  sea.  The  shapes 
and  depths  of  these  inlets  are  in  some  cases  so  rapidly 
altered  by  the  tidal  currents  that  it  is  impossible  to  fore- 
tell for  any  length  of  time  where  vessels  can  find  the 
best  channel.  Thus  the  inlets  must  be  left  uncharted  and 
local  pilots  relied  upon.  Bars  which  cannot  be  crossed 
except  at  high  tide  often  make  moon  time,  not  sun  time, 
the  determining  factor  in  the  sailing  schedules  of  vessels 


304 


FIRST   YE£R   SCIENCE 


leaving  and  entering  port.  The  general  set  of  the  shore 
currents  has  an  effect  upon  the  position  and  shape  of 
these  inlets,  deflecting  the  openings  in  the  direction  of 
their  flow.  They  may  also  singularly  modify  the  outlines 
of  the  reefs  themselves  as  in  the  formation  of  the  three 
much  dreaded  capes  off  the  coast  of  North  Carolina. 

144.  Depressed  Coast.  —  Experiment  127.  —  Cover  a  small  board 
with  a  piece  of  thin  oilcloth  which  has  been  most  irregularly  crumpled. 
Take  the  board  by  one  edge  and  inclining  it  slightly  gradually  sub- 
merge it  in  a  dish  of  water.  What  kind  of  a  line  does  the  water  form 
where  it  meets  the  oilcloth?  In  what  way  would  this  line  change  if 
the  oilcloth  were  more  crumpled?  If  it  were  less  crumpled?  If  the 
board  is  more  submerged,  does  the  position  of  the  water  line  change  ? 
Why  does  its  form  materially  alter? 


PART  OF  THE  COAST  OF  MAINE. 
A  fine  example  of  depressed  coast. 


Along  a  coast  which  has  been  depressed,  the  shore  line 
has  moved  landward  and  a  surface  rendered  irregular  by 
erosion  is  lapped  by  the  inflowing  water.  All  the  ir- 


DEPRESSED   COAST  305 

regularities  which  lie  below  the  water  level  are  filled 
with  water  and  the  shore  line  bends  seaward  around  the 
projecting  elevations  and  landward  into  the  gullies  and 
valleys.  •  Isolated  elevations  surrounded  by  land  low 
enough  to  be  covered  by  the  inflowing  water  have  now 
become  islands. 

The  river  valleys  which  crossed  the  region  now  sub- 


A  NORWAY  FIORD. 

merged  reveal  themselves  only  to  the  sounding  line,  their 
landward  extensions  forming  estuaries  up  which  the  tide 
sweeps  far  into  the  land.  Their  unsubmerged  portions  con- 
tain fresh-water  streams,  the  size  of  which  seems  insignifi- 
cant when  compared  to  the  size  of  the  estuary.  Sheltered 
coves  and  harbors  abound,  affording  protection  to  all  kinds 
of  crafts  and  fitting  these  coasts  to  be  of  great  commercial 
importance. 

The  harvest  of  the  sea  replaces  what  might  have  been 


306 


FIRST   YEAR   SCIENCE 


A  NORWAY  FIORD. 

Showing  large  vessels  anchored  near  the 
shore. 


the  harvest  of  the  land.  The  distance  along  the  coast  be- 
tween two  points  is  much  longer  than  the  straight  line  dis- 
tance over  the  sea.  The 
boat,  not  the  wagon, 
becomes  the  important 
vehicle  of  travel.  Many 
submerged  coasts,  such 
as  those  of  Maine, 
Alaska  and  Norway, 
have  been  modified  by 
ice  action.  Their  val- 
leys have  been  smoothed 
and  rounded. 

In  Norway  the  deep 
fiords  conduct  the  sea 
from  the  island-studded 

coast  far  into  the  interior.  Their  sides  rise  steeply, 
sometimes  for  several  thousand  feet  from  the  water's 
edge  and  descend  so  steeply  below  it  that  large  vessels 
can  be  moored  close  to 
the  shore.  Generally 
there  is  not  sufficient 
level  land  along  the 
sides  of  the  fiord  for 
building  roads.  The 
villages  are  usually  sit- 
uated where  a  side 
stream  has  built  a  little 
delta,  or  at  the  heads  of 
the  fiords  where  the 
unsubmerged  portion  of 
the  valley  begins.  • 

These  U-shaped  valleys  with  their  small  streams  extend 
back  to  the  interior  uplands,  sometimes  blocked  toward 


A  NORWAY  VILLAGE. 
At  the  head  of  a  fiord. 


THE  SAFEGUARDING    OF  COASTS  307 

their  heads  by  descending  glaciers.  They  often  have 
hanging  valleys  which  enter  far  up  along  their  sides,  the 
streams  of  which  descend  by  abrupt  falls  and  adorn  the 
dark  rock  walls  with  bands  of  silver  spray. 

It  was  such  a  coast  as  this  which  bred  the  ancient 
Northmen,  to  whom  the  Sea  of  Darkness,  as  they  called  the 
Atlantic,  was  terrorless.  While  less  favored  and  hardy 
sailors  were  dodging  from  bay  to  bay  along  the  shore 
always  in  sight  of  land,  they  were  pushing  boldly  west, 
guided  only  by  the  beacons  of  the  sky,  and  discovering 
Iceland,  Greenland  and  the  American  continent. 

145.  Harbors.  —  The   importance    to   mankind  of   good 
harbors  cannot  be    overestimated.     No  civilized  country 
by  its  own  products  can  fill  all  the  wants  of  its  inhab- 
itants.    Since  earliest  times  man  has  been  a  barterer  of 
goods.     The  sea  offers  him  an  unrestricted  highway  for 
his  traffic.      Harbors  he  must  have  to  load  and  unload  his 
wares  safely. 

Although  many  of  the  best  harbors  of  the  world  are 
found  along  depressed  coasts,  such  as  the  harbors  of  New 
York,  San  Francisco,  London,  Liverpool  and  Bergen,  yet 
there  are  several  other  sorts  of  harbors.  The  delta  of  a 
great  river  may  afford  a  good  harbor,  as  those  of  New 
Orleans  and  Calcutta.  Harbors  may  be  formed  by  sand 
reefs  and  spits,  like  those  of  Galveston,  Provincetown 
and  San  Diego.  The  atolls  of  the  mid-Pacific  and  even 
the  submerged  craters  of  volcanic  islands  afford  safe  rest- 
ing places  where  ships  may  ride  out  the  storms. 

146.  The  Safeguarding  of  Coasts.  —  As  nations  advance 
in  civilization  and  their  commerce  develops,  they  realize 
the  necessity  of  safeguarding  in  every  way  possible  the 
ships  bearing  their  citizens  and  their  wealth.      Thus  a 
great  system  of  weather  signals,  of  lighthouses  and  of  life- 
saving  stations  has  been  established.     From  these  mariners 


308 


FIRST   TEAR   SCIENCE 


may  know  when  it  is  safe  to  leave  port,  may  be  warned  off 
from  dangerous  shores,  and,  when  in  spite  of  all  precau- 
tion their  vessels  become  wrecked,  may  be  rescued  from  a 
watery  grave. 

The   lighthouses   have   lights    of   different   kinds  and 
colors,  some  fixed,  some  flashing,  so  that  when  unable  to 


SAN  FRANCISCO 
A  harbor  due  to  depression  of  the  coast. 

make  out  the  coast  itself,  the  mariner  can  still  know  his  posi- 
tion by  the  kind  of  light  seen.  Indeed  many  wireless  tele- 
graph stations  are  being  equipped  to  communicate  with 
vessels  at  sea  arid  to  inform  them  of  their  position,  the  con- 
dition of  the  shore  and  the  expected  weather.  Even  the 
kinds  of  material  which  form  the  sea  floor  near  the  shore, 
and  which  may  be  brought  up  by  the  mariner's  sounding 


THE  COAST  OF  THE   UNITED  STATES 


309 


apparatus,  are  charted  for  him,  so  that  in  this  way  he  may 
be  helped  to  ascertain  his  position. 

147.  The  Coast  of  the  United  States.  — The  coast  of  the 
United  States  presents  a  great  variety  of  features.  It  has 
long  stretches  of  uplifted,  depressed  and  fiorded,  dune- 
bordered,  rock-bound,  coral-  and  mangrove-fringed  coasts. 


HARBOR. 


One  of  the  finest  harbors  in  the  world. 


Along  part  of  its  sea  border,  harbors  are  abundant  while 
in  other  portions,  harbors  are  almost  entirely  lacking.  Its 
recently  uplifted  western  coast  has  still  more  recently 
been  slightly  depressed,  thus  forming  the  harbors  of  San 
Francisco,  Portland  and  Seattle.  This  coast  and  the  de- 
pressed and  fiorded  region  of  Alaska  are  paralleled,  but 
in  no  way  duplicated,  by  the  elevated  south  Atlantic 


310 


FIRST   YEAR   SCIENCE 


coast  which  has  more  recently  been  depressed  in  the 
Chesapeake  Bay  region,  and  by  the  depressed  and  slightly 
fiorded  coast  of  northern  New  England.  '•  On  the  eastern 
side  of  the  United  States  a  broad  coastal  plain  has  been 

formed  which  has  no 
counterpart  on  the  west. 
148.  Influence  of  Coast 
Conditions  upon  Inhabit- 
ants. —  All  natural  fea- 
tures have  a  greater  or 
less  influence  upon  the 
inhabitants  of  the  earth, 
but  perhaps  none  has  so 
directly  and  obviously 
influenced  man's  activi- 
ties as  has  the  kind  of 
coast  on  which  he  lives. 
Europe,  with  its  harbor- 
full  and  Africa  with  its 
almost  harbor-less  coasts 
are  in  striking  contrast 
to  each  other.  This 
difference  between  the 
inducements  to  travel 
and  commerce  which 
the  two  continents 
afford  is  one  of  the 
factors  in  producing 
the  marked  difference 
in  progress  attained  by  the  people  of  the  two  continents. 
They  stand  to-day  as  types  on  the  one  hand  of  economic 
progress  and  on  the  other  of  stagnation. 

The  Phoenicians,  the  Carthaginians,    the    Greeks,    the 
English  and  the  other  great  nations  of  the  world  have 


MINOT'S  LEDGE  LIGHTHOUSE. 


SUMMARY  311 

felt  the  enticing  allurement  of  a  captive  sea  waiting  in 
their  harbors  like  a  steed  for  them  to  mount  and  ride 
away  in  quest  of  the  world's  best.  Thus  they  have  ex- 
tended their  conquest  and  influence  far  beyond  the  home- 
land. From  the  time  of  Peter  the  Great,  the  efforts  of 
Russia  to  gain  suitable  outlet  to  the  sea  show  the  impor- 
tance placed  by  progressive  communities  upon  ocean 
traffic.  The  struggle  of  all  the  great  world  powers  to 
strengthen  their  navies,  no  matter  what  the  cost,  shows 
with  what  jealousy  the  products  of  their  ports  are 
guarded. 

Coasts  with  harbors  give  their  people  the  facilities  and 
inducements  for  seeking  the  unknown,  while  the  harbor- 
less  coasts  confine  the  aspirations  of  their  inhabitants  to 
the  products  immediately  around  them.  A  glance  at  the 
coast  line  and  harbors  of  Greece  shows  one  cause  of  its 
ancient  civilization  and  a  reason  why  the  Greeks  were 
" always  seeking  some  new  thing." 

Summary.  —  A  glance  at  a  map  shows  the  great  variety 
of  coast  lines.  The  waves  and  tides  are  constantly  cutting 
and  wearing  the  coast.  The  material  thus  cut  away  is 
ground  fine  and  spread  out  by  the  currents  in  bars  and 
beaches,  filling  up  coves  and  straightening  the  coast. 
Thus  one  of  the  results  of  these  erosive  forces  is  to  make 
the  coastline  more  regular. 

Coastlines  are  affected  not  only  by  wind  and  water 
erosion,  but  by  elevation  and  depression.  When  the 
shore  rises,  or  is  elevated,  part  of  the  comparatively  even 
level  of  the  continental  shelf  becomes  the  coastline.  Thus 
elevated  coasts  are  usually  regular.  But  when  the  shore 
is  depressed,  the  irregularities  caused  by  the  surface 
erosion  on  land  make  bays  and  estuaries.  Thus  depressed 
coasts  are  usually  irregular  and  offer  the  best  harbors. 


312  FIRST  YEAR   SCIENCE 

'  *  ,  v* 

Wherever  there  are  good  harbors  we  find  seafaring 
people.  To  make  ocean  traffic  safe,  seas  are  charted,  coasts 
mapped,  lighthouses  built  and  life-saving,  stations  main- 
tained. Water  transportation  is  the  cheapest,  so  good 
harbors  are  needed  by  all  commercial  nations.  Nations 
with  seacoast  and  harbors  are  usually  more  progressive 
and  more  civilized  than  inland  nations. 


QUESTIONS 

Of  what  do  the  borders  of  different  coasts  consist? 
What  do  the  waves  do  to  the  coast? 
How  are  beaches  and  bars  made  ? 

What  form  do  the  waves  and  currents  tend  to  give  to  the  coast  ? 
How  can  it  be  shown  that  coasts  are  subject  to  changes  in  position 
in  respect  to  the  surface  of  the  sea  ? 

What  are  the  characteristics  of  an  elevated  coast? 

What  are  the  characteristics  of  a  depressed  coast? 

How  are  harbors  formed  ? 

How  are  coasts  safeguarded  ? 

What  kinds  of  coasts  are  found  in  the  United  States? 

How  have  coast  conditions  influenced  their  inhabitants? 


CHAPTER  X 

WATER  SCULPTURE 

149.  Rainfall.  —  The  water  of  the  earth's  surface  is  con- 
stantly evaporating,  rising  into  the  air  and  being  dis- 
tributed by  the  winds.  Much  of  this  water  is  blown  over 
the  land,  where  it  is  condensed  and  falls  as  rain.  Some 


A  HOT  SPRING  IN  THE  YELLOWSTONE. 

portions  of  the  land  receive  much  and  some  little  of  this 
aerial  water  circulation.  When  winds  from  warm  seas, 
where  the  evaporation  is  great,  strike  lofty  mountain 
ranges,  the  land  upon  the  windward  side  has  a  large  rain- 
fall, but  that  upon  the  lee  side  comparatively  little.  This 
is  particularly  well  shown  in  the  northwestern  part  of  the 
United  States.  Since  continents,  as  a  rule,  have  their 

313 


314 


FIRST   YEAR   SCIENCE 


mountains  near  their  borders  it  happens  that  most  conti- 
nental interiors  are  comparatively  dry. 

Regions  over  which  the  prevailing  winds  blow  from  a 
colder  to  a  warmer  latitude  have  little  rainfall,  as  the 
air  is  continually  having  its  capacity  to  hold  moisture  in- 
creased by  its  rise  in  temperature.  This  is  well  illustrated 
in  the  Sahara  region.  Accordingly,  the  amount  of  rainfall 
in  different  parts  of  the  earth  varies  greatly.  In  eastern 
India  south  of  the  Khasi  Hills  a  "record"  fall  of  over 
50  feet  was  recorded  in  one  year,  while  in  desert  regions  a 
year  may  go  by  without  any  fall  of  rain. 

In  the  U  nited  States  the  greatest  rainfall,  over  80  inches, 


Fig.   111. 

is  found  along  the  northwest  coast  and  the  least  in  the  Basin 
Region  of  Utah,  Arizona  and  Nevada.  Whether  rain  falls 
in  large  or  small  quantities,  its  effect  is  always  marked. 
Without  it  the  surface  of  the  ground  is  a  parched  and 
barren  waste  of  dust  and  rock,  with  it,  a  green  and  varied 
expanse  of  never  failing  beauty. 

150.  The  Sphere  of  Activity  of  Rain.  — When  rain  falls 
upon  the  ground,  it  may  do  one  of  three  things.  It  may 
evaporate  immediately  from  the  surface  and  return  to  the 
air ;  or  it  may  run  rapidly  off  the  surface  and  quickly  join 
the  streams  and  rivers  which  bear  it  to  its  final  goal,  the 
sea ;  or  it  may  sink  into  the  ground.  In  this  last  case 
part  of  it  returns  gradually  through  capillary  action  to  the 
surface  where  it  is  again  evaporated;  part  finds  its  way 


SUB-SURFACE   WATER 


315 


into   springs;    and    part   sinks   deep   into   the    soil    and 
rock. 

Which  of  these  courses  the  greatest  part  of  the  rainfall 
will  take  depends  entirely  upon  the  condition  of  its  fall 
and  the  kind  of  surface  upon  which  it  falls.  If  the  rain- 
fall comes  down  rapidly, 
the  larger  part  of  it 
will  immediately  run 
off;  if  it  comes  down 
gently,  much  of  it  will 
sink  into  the  ground. 
If  it  falls  in  forest  re- 
gions or  where  there  is 
much  verdure,  its  flow 
will  be  impeded  by  the 
plants  and  roots.  If 
the  surface  upon  which 
it  falls  is  hard-packed 
and  impervious,  most  of 
'it  will  run  off,  but  if  it 
is  loose  and  easily  pene- 
trated, much  of  it  will 
sink  into  the  soil.  Even 
in  the  dry  parched  sands 
of  the  desert,  however, 

the  rain  falls  sometimes  in  such  cloud-burst  torrents  that 
it  runs  off  in  rushing  streams. 

151.  Sub-Surface  Water  or  Ground  Water.  —  The  rain  that 
sinks  into  the  ground  descends  slowly  along  the  little 
cracks  or  between  the  particles  of  soil  until  it  reaches  a 
point  where  it  can  sink  no  further,  or  until  it  finds  an 
opening  through  which  it  can  flow  out  to  the  surface  at  a 
point  lower  than  where  it  entered.  Here  it  may  ooze 
slowly  out,  or  it  may  be  concentrated  in  a  spring. 


FLOWING  ARTESIAN  WELL. 


316 


FIRST   TEAR   SCIENCE 


If  the  water  which  comes  to  the  spring  has  penetrated 

below  the  surface  far 
enough-to  get  away  from 
the  heating  effect  of  the 
sun,  it  will  be  compara- 
tively cool  when  it  again 
emerges,  and  it  will  form 
a  cold  spring.  If,  how- 
ever, in  the  region  where 
the  spring  occurs  the 
rocks  are  hot  at  the 
depth  to  which  the 
water  penetrated  before 
it  found  a  crack  through 

A  LIMESTONE  CAVE.  which  H  COuld   COme  to 

the  surface  of  the  land, 

then  it  will  become  heated  and  will  form  a  hot  spring. 


MONTEZUMA'S  WELL. 
This  famous  water  hole  is  due  to  the  dissolving  of  the  underlying  rock  layer. 

As  the  crust  of  the  earth  is  in  many  places  composed 
of  rocks  in  layers,  the  rain  often  falls  upon  the  top  of  a 


SUB-SURFACE   WATER 


317 


SINK-HOLE  IN  TENNESSEE  LIMESTONE. 

folded  porous  rock  layer,  below  which  is  a  rock  through 
which  it  cannot  penetrate.  The  water  will  then  accumu- 
late throughout  the  porous  rock.  If  this  rock  layer  in 
another  part  of  its  extent  is  overlaid  by  an  impermeable 


GREAT  NATURAL  BRIDGE,  UTAH. 


318  FIRST  YEAR  SCIENCE 

'      '        .  V* 

layer,  its  water  is  held  in  by  the  impermeable  rocks  above 
and  below,  and  so  is  under  hydraulic  pressure.  When  a 
hole  is  made  in  the  upper  rock  layer  (Fig.-  Ill),  the  water 
will  flow  to  the  surface  and  if  the  pressure  is  sufficient,  it 
may  gush  out  of  the  hole. 

Borings  of  this  kind  form  what  are  called  artesian  wells. 
These  are  of  great  importance  in  many  regions  where  it  is 


NATURAL  BRIDGE,  SAXONY. 

difficult  to  obtain  sufficient  surface  water.  In  some  of  our 
western  states  the  water  from  artesian  wells  has  been  ob- 
tained in  sufficient  quantity  for  extensive  irrigation. 
Although  this  water  often  contains  minerals  in  solution,  it 
is  free  from  surface  contamination  and  is  therefore  usually 
healthful  for  drinking. 

In  some  places  the  surface  water  penetrates  into  layers 
of  rock  which  it  can  dissolve,  such  as  salt  or  limestone. 
Here  it  forms  caves  and  caverns,  the  solid  material  which 


GEYSERS  319 

occupied  the  place  of  the  cave  having  been  carried  away 
in  solution  by  the  water.  There  are  thousands  of  caves 
of  this  kind  but  perhaps  the  most  noted  in  this  country 
are  Mammoth  Cave  with  its  nearly  200  miles  of  under- 
ground avenues  and  grotesquely  sculptured  halls,  and 
Luray  Cave  with  its  wonderful  stalactite  and  stalagmite 
decorations.  Sometimes  the  top  of  one  of  these  caves  is 
nearly  eroded  away,  leaving  a  part  of  its  old  roof  standing 
as  a  natural  bridge,  such  as  the  natural  bridge  of  Virginia 
or  of  Utah.  Sometimes  the  top  falls  in,  leaving  a  sink-hole. 

152.  Geysers.  —  Experiment  128.  —  Fit  a  250  cc.  glass  flask  with  a 
two-hole  rubber  stopper.  Through  one  hole  extend  a  glass  tube 
(a)  almost  to  the  bottom  of  the  flask 
and  through  the  other  hole  a  tube  (b)> 
5  or  6  cm.  longer  than  the  height 
of  the  flask,  to  within  about  1  or  2 
cm.  of  the  bottom  of  the  flask.  This 
last  tube  should  be  slightly  drawn 
out  at  the  end  and  bent  at  the  top  so 
that  it  slants  away  from  the  flask. 
Arrange  the  flask  on  a  ring  stand 
so  that  it  can  be  heated  by  a  Bunsen 
burner.  Connect  to  the  tube  (a)  a 
rubber  tube  long  enough  to  reach  into 

a  water  reservoir  placed  higher  than  the  top  of  the  flask  and  to 
one  side.  Fill  the  reservoir  with  water. 

Through  the  tube  (b)  suck  the  air  out  of  the  flask  until  the 
water  from  the  reservoir  begins  to  run  into  the  flask.  A  siphon  will 
be  formed  which,  when  there  is  no  internal  pressure,  will  keep  the 
water  in  the  flask  slightly  above  the  bottom  of  the  tube  (b).  Now 
heat  the  flask.  When  steam  begins  to  form,  hot  water  will  be  thrown 
out  of  the  tube  (b)  until  its  lower  end  becomes  uncovered  arid  the 
pressure  of  the  steam  relieved.  Water  from  the  reservoir  will  then 
run  in  again  slightly  covering  the  end  of  the  tube.  As  soon  as 
more  steam  is  formed,  hot  water  will  be  ejected  as  before.  Thus  a 
spray  of  hot  water  is  intermittently  ejected  from  the  flask  as  long  as 
heating  continues.  We  have  here  an  action  which  resembles  that  of 
a  geyser.  ' 


320 


FIRST   YEAR   SCIENCE 


In  the  north  island  of  New  Zealand,  in  Yellowstone  Na- 
tional Park  and  in  Iceland,  remarkable  spouting  springs 
called  geysers  are  found.  These  places  -have  had  recent 
volcanic  activity.  The  eruption  of  a  large  geyser  is  a 
most  picturesque  and  startling  phenomenon.  Almost 
without  warning  there  is  thrown  into  the  air  a  column 

of  hot  water  from  which 
the  steam  escapes  in 
rolling  clouds.  It  rises 
in  some  cases  to  a  height 
of  a  hundred  feet  or 
more  and  is  maintained 
at  nearly  this  height  by 
the  ceaseless  outrushing 
of  the  water  for  a  time 
varying  from  a  few  min- 
utes to  between  one  and 
two  hours.  Then  it 
gradually  quiets  down 
and  dies  away  into  a 
bubbling  spring  of  hot 
water. 

The  time  at  which 
most  geysers  will  erupt 
is  uncertain,  but  there 
is  one,  Old  Faithful,  in 
Yellowstone  Park,  which 

is  almost  as  regular  as  a  clock,  the  time  between  its 
eruptions  being  a  little  over  an  hour.  This  geyser  plays 
to  the  height  of  about  150  ft.  and  maintains  the  column 
of  water  for  about  four  minutes.  The  Giant  Geyser  of 
the  same  region  throws  a  large  column  of  water  to  a 
height  of  250  ft.  It  plays  from  one  to  two  hours. 

The  outpouring  hot  water  brings  up  with  it  dissolved 


GIANT  GEYSER  IN  ERUPTION. 


GEYSERS 


321 


rock  and  as  the  spray  falls  back  and  cools,  this  is  deposited, 
forming  craters  of  singular  shape  and  grotesque  beauty. 
On  looking  into  these  craters  a  smoothly  lined,  irregular, 
crooked,  tubelike  opening  is  seen  to  extend  down  into 
the  ground.  It  is  through  this  that  the  water  finds  its 
way  to  the  surface.  How  long  these  tubes  are  nobody 
knows,  but  they  must  reach  to  a  point  where  the  heat  is 


CONE  OF  THE  BEEHIVE  GEYSER. 
Built  from  the  dissolved  material  brought  up  by  the  hot  water. 

sufficient  to  raise  water  to  its  boiling  point.     This  heat  is 
probably  due  to  hot  sheets  of  lava. 

When  the  water  in  the  tube  is  heated  enough  to  make 
it  boil  under  the  pressure  to  which  it  is  subjected,  steam 
forms  and  some  of  the  water  is  pushed  out  over  the  sur- 
face. This  escape  of  water  relieves  some  of  the  pressure, 
and  more  of  the  water  far  down  in  the  tube  expands  into 
steam  thus  throwing  more  water  out.  Huge  indeed  must 
be  the  reservoir  to  which  the  tube  in  a  geyser  like  the 
Giant  leads,  to  be  able  to  pour  out  such  a  vast  quantity 
of  water. 


322 


FIJtST   YEAR   SCIENCE 

' 


153.  Run-off.  —  The  rain  that  falls  upon  the  land  and 
neither  evaporates  nor  sinks  into  the  surface  runs  off  as 
fast  as  it  can  toward  the  sea.     It  is  joined'  sooner  or  later 
by  the  water  from   the  springs  and  by  the  rest  of  the 
underground  drainage.     Sometimes  the  journey  is  long 
and  there  are  many  stops  and  delays  in  lakes  and  pools ; 
sometimes  the  course  is  quite  direct  and  quickly  traveled. 
The  run-off  most  profoundly  affects  the  earth's  surface. 
Gullies  and  valleys  are  cut,  depressions  are  filled  ;   in  fact, 
running  water  is  the  chief  tool  which   has   carved  the 
features  of  the  earth.     It  has  had  a  long  time  to  act  and 
it  has  kept  unremittingly  busy,  so  that  the  results  of  its 
action  appear  now  in  our  varied  landscape. 

154.  Pools  and  Lakes.  —  The  water  which  runs  off  the 
surface  first  fills  the  depressions.     As  soon  as  these  are 

filled,  it  runs  over  the 
lowest  part  of  their  rims 
and  starts  again  on  its 
course  to  the  greatest  of 
all  depressions,  the  sea. 
If  depressions  of  con- 
siderable size  become 
filled  with  water,  we 
call  them  lakes.  As 
with  mountains,  the 
term  lake  gives  no  defi- 
nite idea  as  to  size.  In  some  localities  a  water  surface 
of  a  few  acres  is  called  a  lake,  while  in  other  localities, 
the  area  must  be  several  square  miles  to  merit  this  name. 
As  a  rule,  when  the  area  covered  by  water  is  small,  it 
is  called  a  pool  or  a  pond. 

The  streams  that  fiow  into  lakes  are  continually  bring- 
ing down  the  sand  and  mud  they  have  gathered  in  their 
course,  and  are  thus  filling  up  the  lakes.  Lake  Geneva  in 


AN  UNDRAINED  UPLAND. 


POOLS  AND  LAKES  323 

Switzerland  has  had  its  narrow  eastern  end  filled,  for  a 
distance  of  fifteen  or  more  miles,  with  the  coarse  sediment 
brought  down  by  the  Rhone.  The  whole  basin  of  the 
lake  has  been  covered  to  an  unknown  depth  by  the  finer 
sediment.  The  outlet  to  a  lake  tends  to  wear  away  its 
bed,  but  it  does  this  slowly,  as  it  has  little  sediment  with 


SUNSET  ON  GREAT  SALT  LAKE. 

which  to  scour.  Thus  lakes  are  being  constantly  both 
filled  and  drained,  and  so  are  comparatively  short-lived 
features  of  the  earth.  Rivers  which  have  lakes  along  their 
courses  must  be  young  as  otherwise  they  would  have  filled 
or  drained  the  lakes. 

Lakes  are  very  important  features  to  man.  They  filter 
river  water  so  that  rivers  emerging  from  lakes  are  clear. 
Where  the  Rhone  enters  Lake  Geneva,  it  is  turbid  and 


324 


FIRST   YEAR   SCIENCE 


full  of  silt,  but  when  it  emerges,  it  is  clear  and  without 
sediment.  Lakes  also  act  as  reservoirs  for  the  water  that 
pours  into  them  at  the  time  of  freshets.  Rivers  emerging 
from  lakes  of  considerable  size  vary  little  in  the  height  of 
their  water  at  different  seasons  of  the  year.  They  are 
without  floods.  The  St.  Lawrence  illustrates  this.  On 
the  other  hand  the  Ohio  with  its  frequent  and  terribly  de- 
structive floods  shows  the  effect  of  unrestrained  run-off. 


THE  DEAD  SEA. 

Lakes  often  form  most  valuable  internal  waterways,  as 
in  the  case  of  the  Great  Lakes  and  the  Caspian  Sea. 
Lakes  are  also  most  beautiful  objects  on  the  landscape 
and  their  rippling  waters  give  joy  and  pleasure  to  thou- 
sands. 

In  some  regions  the  rainfall  is  so  small  that  the  depres- 
sions never  fill  up  sufficiently  to  overflow  their  rims.  The 
water  is  evaporated  from  the  surface  as  fast  as  it  runs 
into  the  lake.  Thus  all  the  salt  and  other  soluble  sub- 


THE   WORK   OF  RUNNING    WATER 


325 


stances  which  have  been  extracted  from  the  land  and 
brought  into  the  lake  by  the  rivers  remain  there,  since 
only  pure  water  is  evaporated.  In  this  way  lakes  with- 
out outlet  become  salt.  Great  Salt  Lake  in  Utah  is  an 
example  of  this.  Some  salt  lakes,  like  the  Caspian  Sea, 
were  probably  once  a  part  of  the  ocean,  so  that  they  have 
always  been  salt. 

As  time  goes  on,  more  salt  is  brought  to  these  lakes 
without  outlets,  and  they  become  more  and  more  salty. 


LAKE  DRUMMOND. 
A  lake  in  Dismal  Swamp,  Virginia,  which  is  being  filled  by  vegetable  growth. 

Great  Salt  Lake  has  something  like  14  or  15  %  of  solid 
material  in  its  water  and  the  Dead  Sea  about  25  %.  An 
effort  to  swim  in  these  waters  gives  one  an  exceedingly 
queer  sensation.  The  buoyancy  is  so  great  that  a  large 
part  of  the  body  is  out  of  water,  and  one  finds  oneself 
bobbing  around  like  a  cork. 

Depressions  that  are  very  shallow  and  are  largely  filled 
with  vegetable  growths  are  called  swamps. 

155,  The  Work  of  Running  Water. — Running  water  has 
the  power  of  carrying  solid  materials.  If  it  is  moving 
slowly,  this  power  is  not  great ;  if  moving  swiftly  and  in 
great  volume,  it  is  tremendous.  The  carrying  power  of  a 


326  FIRST   YEAE   SCIENCE 

stream  increases  very  rapidly  if  its  velocity  is  increased. 
A  stream  having  its  velocity  doubled  will  carry  several 
times  as  much  material  as  before.  Thus  it  happens  that 
water  running  over  a  surface  sweeps  loose  material  with 
it,  the  amount  varying  with  the  rapidity  and  volume  of 
the  flowing  water. 

As  this  loose  material  sweeps  over  solid  surfaces,  it  cuts 


GULLIES  BEING  CUT  BY  RUNNING  WATER. 

them  down.  Thus  flowing  water  is  continually  wearing 
down  and  sweeping  away  the  surface  over  which  it  moves. 
This  sort  of  work  is  called  water  erosion. 
%  When  running  water  is  concentrated  into  a  stream,  the 
work  of  erosion  is  also  concentrated  and  the  wearing  down 
of  the  stream  bed  becomes  comparatively  rapid.  This 
cutting  down  goes  on  irregularly,  being  greatest  at  time 
of  flood  and  least  when  the  flow  is  slight.  It  is  estimated 
that  the  solid  material  carried  by  the  Mississippi  River 


THE  WORK  OF  SUNNING  WATER 


327 


from  its  basin  lowers  the  basin  about  one  foot  in  5000 
years;  but  the  material  which  is  dissolved  increases  the 
amount  carried  away,  so  that  the  basin  is  lowered  a  foot 
in  from  3000  to  4000  years. 


THE  BAD  LANDS  OF  DAKOTA. 
Kunning  water  has  so  dissected  this  land  as  to  render  it  valueless. 

The  channels  of  some  of  the  streams  in  this  basin  are 
cutting  down  with  far  greater  rapidity  than  this.  We 
see  gullies  cutting  down  little  troughs  for  themselves 
several  inches  deep  in  one  rainstorm.  The  rapidity  of 
cutting  depends  upon  the  material,  the  slope  and  the 
quantity  of  water.  That  "  the  waters  wear  the  stones " 
was  noted  even  in  Job's  time. 


328  FIRST   YEAR   SCIENCE 

When  rain  falls  upon  a  sloping  surface  of  fine  textured, 
easily  eroded  material  not  covered  thickly  with  vegetation, 
this  will  be  deeply  and  fantastically  sculptured.  An  excel- 
lent example  of  this  kind  of  sculpturing  is  found  in  the 
Bad  Lands  of  Dakota.  Here  travel  is  exceedingly  difficult. 
It  was  in  these  natural  fastnesses  that  the  Sioux  Indians 
made  their  last  ineffectual  stand  against  the  white  man's 
civilization. 


DIVIDES  BETWEEN  STREAMS. 

The  ridge  in  the  center  of  the  picture  separates  two  streams  flowing  in 
opposite  directions. 

156,  Divides.  —  If  we  carefully  observe  the  drainage  of 
a  region,  we  find  that  the  areas  from  which  different 
streams  gather  their  water  are  usually  so  distinctly  sepa- 
rated from  one  another  that  a  line  could  be  drawn  so  that 
wherever  water  falls  the  rivulets  on  one  side  would  flow 
into  one  stream  and  on  the  other  side  into  another.  Such 
a  line  of  the  highest  land  between  the  drainage  areas  of 
neighboring  streams  is  called  a  divide.  The  line  may  be 


FALLS  AND  RAPIDS  329 

very  distinctly  marked,  as  on  mountain  ridges,  or  it  may 
be  difficult  to  determine,  as  in  a  flat  country,  but  if  the 
drainage  is  well  established,  it  will  be  apparent. 

If  the  drainage  is  not  well  established,  areas  may  be 
found  which  at  one  time  drain  in  one  direction  and  at  an- 
other time  in  another.  A  singular  example  of  the  shift- 
ing flow  of  a  drainage  area  is  found  in  Yellowstone  Park 
where  Two-ocean  Creek  shifts  from  one  side  to  the  other 
of  a  fan  it  has  built,  and  at  one  time  delivers  its  drainage 
into  the  Atlantic  Ocean  and  at  another  time  into  the 
Pacific. 

Near  the  dividing  line  between  two  drainage  areas, 
swamps  sometimes  occur,  which  have  streams  flowing 
from  them  in  two  directions  so  that  part  of  their  water 
goes  to  one  stream  and  part  to  another.  But  as  these 
swamps  become  better  and  better  drained,  each  stream 
will  carry  off  its  definite  part  of  the  water.  Divides  are 
irregular  in  their  height,  so  that  roads  and  railways  in 
passing  from  one  drainage  basin  to  another  usually  seek 
out  the  lowest  part  of  the  divide.  In  mountain  regions 
these  low  places  are  called  passes. 

Divides  do  not  always  remain  in  the  same  place,  as  the 
river  on  one  side  may  from  some  cause  become  able  to 
carry  off  the  drainage  more  easily  than  the  river  on  the 
other  side.  It  will  thus  push  back  its  headwaters  and 
shift  the  divide  back  until  the  divide  becomes  adjusted  to 
the  abilities  of  the  two  rivers. 

157.  Falls  and  Rapids.  —  In  many  streams  the  flow  of 
water  is  interrupted  by  falls  and  rapids.  Sometimes 
the  course  of  a  stream  is  crossed  by  a  great  break  in  the 
earth's  crust,  one  side  of  which  has  been  raised  above  the 
other.  This  makes  a  fall,  or,  if  the  stream  is  able  to  cut 
down  fast  enough,  a  rapid.  Falls  or  rapids  of  this  kind 
have  been  produced  in  the  Colorado  River. 


330 


FIRST   YEAR   SCIENCE 


YOSEMITB  FALL. 
One  of  the  most  beautiful  falls  in  the  world,  due  to  glacial  action. 

Sometimes  the  course  of  a  stream  is  changed,  as  was  the 
case  with  many  of  the  streams  in  the  northern  part  of 
North  America  at  the  time  of  the  Glacial  Period.  In  its 


FALLS  AND  RAPIDS  331 

new  course  the  stream  may  fall  over  a  cliff,  as  did  Niagara 
River  which  used  to  fall  into  Lake  Ontario  over  the  cliff 
near  where  Lewiston  is  now  located.  Here  was  developed 
a  great  fall  which,  owing  to  the  kind  and  position  of  the 
rocks  over  which  the  river  flowed,  has  moved  back,  leav- 
ing a  gorge  about  seven  miles  long. 

The  rock  layers  are  nearly  horizontal  with  a  hard  layer 
at  the  top  and  softer  layers  below.  As  the  water  strikes 
the  foot  of  the  falls  it  drives  rebounding  currents  against 
the  rock  wall  behind  it,  and  wearing  away  the  softer  rock 
undermines  the  harder  rock  at  the  top,  which  breaks  off  in 
great  blocks.  Thus  the  falls  maintain  an  almost  vertical 
wall  behind  them.  These  falls  are  about  160  feet  high, 
one  of  the  grandest  of  nature's  wonders  and  one  of  the 
greatest  sources  of  water  power  in  the  world. 

Falls  or  rapids  may  also  be  formed  in  a  stream  where  it 
passes  from  harder  to  softer  material,  as  from  the  old  land 
to  the  coastal  plain.  The  softer  material  is  worn  away 
faster  than  the  hard  material  and  the  stream  bed  lowered 
more  rapidly,  thus  forming  a  precipitous  descent.  Falls 
of  this  kind  were  also  formed  where  the  glacial  ice  forced 
the  streams  to  make  new  channels  for  themselves  across 
the  upturned  edges  of  layers  varying  in  hardness. 

The  falls  in  the  northern  part  of  the  United  States  were 
most  of  them  formed  by  the  rearrangement  of  the  drain- 
age lines  at  the  close  of  the  Glacial  Period,  and  those  in  the 
southern  part  of  the  country  by  the  more  rapid  wearing 
away  of  the  softer  rocks  of  the  coastal  plain.  Thus  we 
see  that  the  hum  of  the  spindle  and  the  lathe  are  often 
but  the  modulated  whispers  of  those  ancient  forces  which 
thousands  of  years  ago  sorted  the  rock  materials  and  built 
the  vast  continental  ice  palaces  of  the  Glacial  Period. 

Streams  which  have  falls  and  rapids  have  not  flowed  in 
their  present  channels  a  long  time,  as  time  is  reckoned 


332  FIRST  YEAR   SCIENCE 

'   '  •          r* 

in  considering  the  earth's  history.  If  they  had,  the  falls 
and  rapids  would  have  been  worn  back  and  smoothed  out. 
Thus,  falls  and  rapids  are  characteristic *of  young  rivers. 

158.  River  Development.  —  The  rain  which  falls  upon  a 
flat  country  runs  off  very  slowly,  a  large  part  of  it  soak- 
ing into  the  ground.  Pools  and  lakes  are  formed  in  the  in- 
closed basins,  and  sluggish  streams  with  irregular  little 
crooks,  which  show  that  the  streams  have  hardly  decided 


NIAGARA  FALLS. 
A  young  river  cutting  down  a  layer  of  hard  rock. 

where  they  want  to  go,  wander  in  the  slight  depressions 
down  the  gentle  slopes  and  unite  with  other  streams  here 
and  there  until  a  river  of  ever  increasing  size  is  formed. 

In  some  places  the  streams  flow  through  lakes  where 
they  deposit  their  sediment,  thus  filling  the  lake  basins. 
Here  and  there  they  pass  over  hard  layers  of  rock  which 
hold  them  up  in  falls  and  rapids.  These  they  at  once 
begin  to  smooth  down.  Rivers  of  this  kind  may  well  be 
called  young,  as  their  life  work  is  just  beginning.  The 
Red  River  of  the  North,  with  its  shallow  narrow  valley 


RIVER   DEVELOPMENT 


333 


and  tortuous  course,  and  the  Niagara  River,  with  its  lakes 
and  falls,  are  examples  of  young  rivers. 

Where  the  slope  of  the  newly  exposed  surface  is  consid- 
erable, the  streams  flow  much  more  rapidly  and  develop 
their  courses  more  quickly.  The  small  irregularities  are 
sooner  straightened  and  the  trough  deepened,  thus  form- 
ing side  slopes  down  which  run  little  rivulets  which  in 


YELLOWSTONE  RIVER. 
A  young  river  flowing  in  a  deep  trough. 

time  form  side  streams.  The  heads  of  these,  like  the 
heads  of  the  larger  streams,  are  constantly  working  back 
into  the  undissected  area.  Gradually  the  side  streams 
develop  side  streams  of  their  own,  and  almost  the  whole 
surface  is  covered  with  a  network  of  streams. 

As  the  work  of  erosion  goes  on  and  the  streams  deepen 
their  valleys,  only  a  few  imperfectly  drained  remnants  of 
the  former  flat  surface  are  left  here  and  there.  These  lie 
between  the  larger  streams  in  places  which  the  side  streams 


334  FIRST  YEAR  SCIENCE 

*  .         *•* 

have  not  as  yet  been  able  to  reach.  Almost  the  entire 
surface  is  so  intricately  carved  into  drainage  lines,  that 
wherever  water  falls  it  immediately  finds  a  downward 
sloping  surface.  The  main  stream  by  this  time  has  prob- 
ably smoothed  out  most  of  its  falls  and  rapids  and  has  de- 
veloped long,  smooth  stretches. 

Here  it  is  no  longer  cutting  down  its  trough,  but  has 
only  sufficient  slope  to  enable  it  to  bear  along  its  load  of 


A  STREAM  WORKING  BACK  INTO  AN  UNDISSEOTED  AREA. 

waste.  It  here  deposits  upon  its  valley  floor  about  as 
much  as  it  takes  away.  In  this  part  of  its  course  a  river 
is  said  to  be  graded.  The  longer  a  river  flows  undisturbed 
by  any  deformation  of  its  valley,  the  fewer  falls  and  rapids 
it  will  leave  and  the  longer  will  be  its  graded  stretches. 
The  Missouri  River  near  Marshall,  Missouri,  is  an  excellent 
example  of  a  graded  river. 

Sometimes  a  stream  becomes  so  overloaded  with  detritus, 
which  it  has  acquired  in  a  steeper  part  of  its  extent,  or 


EIVER  DEVELOPMENT 


335 


RIVER  EROSION. 
Cutting  down  the  outer  side  of  the  curve  and  depositing  on  the  inner. 

which  has  been  brought  to  it  by  tributaries,  that  it  is  con- 
tinually being  forced  to  deposit  some  of  its  load.  Thus  it 
silts  up  its  course  and  flows  in  a  network  of  interlacing 


THE  PLATTE  RIVER. 


shallow  channels.     The  Platte  as  it  crosses  the  plains  of 
Nebraska  is  an  example  of  such  an  overloaded  river. 
When  a  stream  swings  around  a  curve,  the  swiftest  part 


336  FIRST   YEAR   SCIENCE 

of  the  current  is  on  the  outside  of  the  curve  and  the  slowest 
on  the  inside.  A  river  that  is  carrying  about  all  the  load 
that  it  can,  on  passing  around  a  curvfe,  is  able  in  its 
outer  part  to  carry  more  than  before  and  cuts  into  the 
bank,  while  on  its  inner  part  it  flows  less  rapidly  and  is 
able  to  carry  less,  thus  being  forced  to  drop  some  of  its 
load.  As  a  river  flows  along  its  graded  stretches,  eroding 
in  some  places  and  filling  in  others,  it  broadens  its  valley 


RIVER  PLAIN. 

floor,  leaving  at  the  border  of  its  channel  a  low  plain 
which  in  time  of  flood  may  be  covered  with  water.  Such 
a  river-made  plain  is  called  a  flood  plain. 

If  a  river  once  begins  to  swing  on  its  valley  floor,  it 
continues  to  do  so,  since  whenever  it  strikes  the  bank,  it 
is  reflected  toward  the  other  side,  and  is  made  to  move 
in  the  direction  of  the  opposite  bank  as  well  as  down- 
stream. The  windings  that  it  thus  assumes  on  a  flat 


RIVER  DEVELOPMENT 


337 


valley  floor  are  roughly  S-shaped  and  are  called  meanders, 
from  the  name  of  a  river  in  Asia  Minor  which  was,  in  very 
ancient  time,  noted  for  having  such  swinging  curves.  The 
size  of  these  curves  will  be  proportional  to  the  size  of  the 
river. 

Great  rivers  like  the  Mississippi  have  a  swing  of  several 
miles,  while  a  small  stream  may  have  a  swing  of  only  a 


RlVER   MEANDERING   IN   ITS    FLOOD   PLAIN. 

few  feet  or  rods.  These  meanders  are  continually  chang- 
ing their  shape,  owing  to  the  cutting  and  filling.  Since 
they  strike  the  bank  with  the  greatest  force  on  the  down- 
stream side  of  the  curve,  thejr  also  move  downstream 
themselves.  This  can  be  seen  from  maps  of  the  Missis- 
sippi taken  at  different  times. 

The  meanders  sometimes  become  so  tortuous  that  the 


338 


FIRST   YEAR   SCIENCE 


downstream  side  of  one  curve  approaches  the  upstream 
side  of  another  and  even  cuts  into  it,  thus  causing  the 
river  to  desert  its  curved  path  and 
straighten  itself  at  this  point.  The 
old  deserted  winding  looks  something 
like  an  oxbow,  and  when  filled  with 
water,  is  called  an  oxbow  lake.  Some- 
times the  meanders  are  artificially 
straightened,  as  has  been  done  in  the 
lower  Rhine  valley,  and  much  arable 

THE  MISSISSIPPI  AND       land  reclaimed. 
SOME  OF  ITS  ABANDONED         In   time   of   flood,    \vhen    a    river 
MEANDERS.  spreads  over  its  flood  plain,  the  ve- 

locity of  the  water  is  checked  outside  the  channel  and 
some  of  the  sediment  it  carries  is  deposited.  The  most 
sudden  check  in  velocity  occurs  where  it  leaves  the 


LEVEE  ALONG  THE  LOWER  MISSISSIPPI. 

channel,  so  more  material  will  be  deposited  here  than 
elsewhere  on  the  flood  plain.  The  banks  of  the  channel 
will  thus  be  built  up  more  rapidly,  and  the  flood  plain  near 


RIVER   DEVELOPMENT 


339 


the    river  will   slope   away  from  the  channel   instead  of 
toward  it. 

This  is  well  shown  in  the  lower  Mississippi,  where  the 
river  is  found  to  be  flowing  on  a  natural  embankment,  the 
side  streams  running  away  from  the  river  instead  of  into 
it.  In  some  places  the  embankment  is  fifteen  or  twenty 
feet  above  the  rest  of  the  flood  plain.  These  natural 
levees,  as  they  are  called,  often  force  the  tributary  streams 
to  flow  for  long  distances  upon  the  flood  plain  before  they 


LEVEE  OF  THE  SACRAMENTO. 

can  enter  the  main  river.  The  Yazoo  River  is  forced  to 
flow  along  the  flood  plain  some  200  miles  before  it  can 
enter  the  Mississippi.  Artificial  levees  are  often  built  to 
keep  rivers  from  overflowing  their  flood  plains.  Such  are 
the  high  levees  .along  the  Lower  Mississippi  and  Sacra- 
mento rivers. 

Sometimes  the  flood  plain  of  the  main  river  is  built  up 
more  rapidly  than  the  tributaries  can  build  theirs,  so  that 
they  are  dammed  up  as  they  enter  the  flood  plain  of  the 
main  stream  and  form  a  series  of  fringing  lakes  along  its 
border.  A  fine  example  of  this  is  found  in  the  lower 
course  of  the  Red  River  of  Louisiana. 


340 


FIRST  YEAR   SCIENCE 


A  river  is  said  to  be  mature  when  it  has  reduced  its 
valley  to  grade  and  is  able  to  meander  freely  upon  its 
flood  plain,  its  side  streams  having  appropriated  all  the 
undrained  upland  which  they  are  able  to  obtain.  The 
river  is  now  carrying  off  in  the  easiest  and  most  effective 
way  the  drainage  which  falls  upon  its  drainage  basin. 

When  a  river  has  graded  itself  and  built  its  flood  plain, 


AN  OLD  RIVER. 
This  river  has  done  its  work  and  has  completed  a  cycle  of  erosion. 

its  own  active  work  consists  largely  in  carrying  off  the 
materials  brought  to  it  by  its  side  streams.  Although 
these  are  now  able  to  appropriate  no  new  territory  they 
continue  to  wear  down  the  country  and  round  off  the 
divides  till  the  whole  region,  unless  reelevated,  is  reduced 
to  an  almost  level  plain  with  its  entire  drainage  system 
nearly  at  grade.  Most  of  the  material  now  carried  by  the 
river  is  in  solution,  and  there  is  but  little  erosion.  The 


RIVERS  IN   DRY  CLIMATES 


341 


river  has  accomplished  its  life  work,  it  has  borne  to  the 
sea  all  the  burden  it  has  to  bear,  its  labors  are  ended,  it 
has  reached  old  age.  It  has  reduced  its  drainage  area  to 
a  base  level  of  erosion.  When  a  river  has  thus  done  all 
the  wearing  down  of  which  it  is  capable  it  is  said  to  have 
completed  a  cycle  of  erosion. 

159.    Rivers  in  Dry  Climates.  —  In    a    region   where    the 
climate  is  very  dry,  rivers  are  often  intermittent  in  their 


RESULTS  OF  A  SUDDEN  FLOOD. 

flow.  They  contain  water  only  after  rains.  Such  rivers 
may  dry  up  before  they  reach  any  other  body  of  water, 
their  water  entirely  evaporating  or  sinking  into  the  dry 
soil.  Their  development  is  therefore  somewhat  irregular. 
If  the  slopes  are  steep  and  there  is  little  vegetation  to 
protect  them  and  hinder  the  quick  run-off  of  the  water, 
rivers  flood  very  rapidly,  eroding  their  channels  and  wash- 
ing away  their  banks.  Where  they  descend  upon  level 
ground  they  silt  up  their  old  courses  and  acquire  new 
channels.  Thus  a  river  which  for  the  larger  part  of  the 


342 


FIRST   YEAR  SCIENCE 


year  is  a  mere  brook  may  after  a  rain  become  a  devastat- 
ing torrent,  bursting  its  banks  and  carrying  destruction 
to  settlements  and  farm  lands  along  its'- course.  It  may 
even  change  its  entire  lower  course. 

160.   Accidents    in  River  Development.  —  While  a  river  is 
developing  its  drainage  area  many  accidents  may  happen 

to  it.  The  competition 
of  other  rivers  in  the 
same  region  affect  it. 
The  river  that  has  the 
shortest  course  to  the 
sea  or  the  most  easily 
eroded  bed  has  the  ad- 
vantage. It  lowers  its 
valley  more  rapidly, 
thus  giving  its  side 
streams  steeper  grades 
and  enabling  them  to 
wear  back  faster  into  the  upland,  and  thus  to  gain  more 
than  their  share  of  the  drainage  of  the  region. 

As  soon  as  the  un- 
appropriated drainage 
area  has  been  channeled, 
it  begins  to  push  back 
the  divides  of  its  neigh- 
bors, thus  appropriat- 
ing some  of  the  run-off 
they  may  have  acquired. 
In  Figure  113  a  case 
of  this  kind  is  shown. 
The  river  A.  reaches  the 
sea  by  a  long  course,  Flg'  114' 

while  the  streams  B,  67,  D  have  short  courses.  These 
short  streams  have  steeper  grades  than  A  and  thus  are 


Fig.   113. 


ACCIDENTS  IN  RIVER  DEVELOPMENT 


343 


able  to  gnaw  back  and  cut  down  their  valleys  faster. 
Thus  they  push  the  divide  EF  farther  and  farther 
toward  A. 

In  Figure  114  a  stage  is  shown  in  which  the  divide  has 
been  pushed  back  toward  A  and  at  one  point  has  ap- 
proached very  near  to  the  upper  part  of  the  branch  6r. 
In  Figure  115  it  has  been  pushed  across  this  branch  and 
the  stream  B  has  tapped  G-  and  appropriated  its  head- 
waters. This  is  a  case 
of  what  is  called  behead- 
ing &?  piracy. 

As  A  has  lost  some 
of  its  water  it  erodes 
its  valley  even  more 
slowly  than  before,  and 
a  branch  of  the  stream 
D  may  take  away  the 
headwaters  of  its  branch 
H.  If  time  enough  is 
allowed,  a  branch  of  the 


Fig.   115. 


stream  C  may  completely  behead  A,  leaving  only  its  lower 
trunk  as  an  independent  river.  Cases  of  river  piracy 
are  of  frequent  occurrence. 

A  river  may  by  some  accident  have  its  supply  of  sedi- 
ment greatly  increased,  causing  it  for  a  time  to  build  up 
its  valley  floor  instead  of  eroding  it,  thus  forming  a  filled 
river  valley.  When  the  supply  of  sediment  fails,  the  river 
begins  cutting  down  the  filled  valley,  leaving  terraces 
along  the  sides  to  mark  the  successive  levels  at  which  it 
flowed. 

River  terraces  are  often  very  prominent  along  our 
northern  rivers,  since  by  the  melting  of  the  ice  at  the  close 
of  the  last  Glacial  Period  these  rivers  were  supplied  with  a 
vast  amount  of  sediment  which  they  were  unable  to  carry 


344  FIRST   YEAR   SCIENCE 

"     '      '  jf* 

away  and  so  deposited  on  their  valley  floors.  When  the 
supply  ceased,  they  eroded  their  valleys,  leaving  terraces 
along  the  sides. 

The  region  in  which  a  river  is  situated  may  be  elevated, 
thus  affecting  its  normal  development  and  beginning  a 
new  cycle  in  its  history.  The  elevating  may  take  place 
over  its  whole  drainage  area  or  only  Over  a  part  of  it. 


RIVER  TERRACES. 
The  river  is  now  cutting  down  its  former  plain,  leaving  terraces. 

If  the  whole  region  is  elevated,  the  energy  of  the  entire 
river  is  revived,  and  the  river  may  be  called  a  revived 
river. 

The  elevation  may  take  place  at  any  time  during  the 
history  of  the  river.  If  it  takes  place  after  the  river  has 
become  old  and  is  meandering  on  its  flood  plain,  the  river 
will  begin  afresh  to  cut  down  its  valley.  But  as  its  mean- 
dering course  has  been  established,  the-  trench  that  it  now 
cuts  is  not  like  that  of  a  young  river,  but  is  a  meandering 


INCISED  MEANDERS. 


ACCIDENTS  IN  RIVER  DEVELOPMENT 


345 


trench,  and  what  are  called  intrenched  meanders  are  formed. 
This  region  will  have  the  steep  V-shaped  valleys  charac- 
teristic of  a  young  region  and  the  well-developed  drainage 
and  meandering  rivers  characteristic  of  a  mature  region. 
The  Palmyra,  Virginia,  sheet  shows  these  characteristics. 
The  main  rivers  meander,  in  steep  valleys.  A  profile 
shows  these  valleys  to  be  steep  and  V-shaped  with  broad, 


INTRENCHED  MEANDERS. 

rounded  uplands  between,  well  provided  with  drainage 
channels. 

When  the  elevation  extends  beyond  the  mouth  of 
the  river,  the  river  must  prolong  its  course  over  the 
emerged  land  in  order  to  reach  the  sea.  It  may  happen 
that  rivers  which  formerly  entered  the  sea  at  different 
points,  in  extending  their  courses  over  the  emerging  con- 
tinental shelf,  join  some  large  stream  and  all  enter  the  sea 
through  it. 

This    is    what   happened    to    the    rivers    now    forming 


346 


FIRST   YEAH   SCIENCE 


branches  of  the  lower  Mississippi  when  the  coastal  plain 
bordering  the  Gulf  of  Mexico  was  elevated.  These  for- 
merly entered  the  extended  Gulf  by  separate  mouths,  but 
when  the  land  rose  and  forced  the  water  of  the  sea  back, 
their  extended  courses  joined  them  to  the  great  central 
river,  thus  vastly  increasing  its  drainage  area  and  the 
volume  of  water  it  poured  through  its  mouth  into  the 
sea.  Many  of  the  great  river  systems  of  the  world  have 

been  built  in  this  way. 
These  may  be  called  en- 
grafted rivers. 

In  Figure  116  the 
rivers  all  enter  the  sea 
at  the  old  coast  line  G-H 
by  separate  mouths. 
When  this  region  is 
elevated  so  that  the 
coast  is  at  IK*  the  rivers 
E,  D,  B  find  that  their 
easiest  course  to  the  sea 
is  by  engrafting  them- 
selves upon  the  river  (7, 
and  thus  they  all  four 
The  rivers  F  and  A 


Fig.    116. 


find  their  outlet  at  one  point  L. 

still  maintain  their  independent  courses. 

It  may  be  that  the  elevation  takes  place  over  only  a 
part  of  the  river's  course.  Then  the  river  is  dammed  back 
and  laked  on  the  landward  side  of  the  elevation  and 
obliged  to  seek  a  new  course  for  itself,  thus  becoming  a 
reversed  river,  or  else  it  is  strong  enough  to  cut  its  bed 
down  as  fast  as  the  land  rises,  and  thus  maintain  its  course. 
Such  a  river  is  called  an  antecedent  river,  as  its  course 
antecedes  the  uplift  which  naturally  would  have  deter- 
mined its  course.  The  Columbia  River  has  maintained 


ACCIDENTS  IN  RIVER  DEVELOPMENT 


347 


its  course  through  uplifts  which  have  reached  thousands 
of  feet. 

Not  only  may  a  river  be  elevated,  but  it  may  be  de- 
pressed. In  this  case  its  rate  of  erosion  is  diminished, 
and  the  river  becomes  marshy  where  the  grade  is  low. 
Where  the  river  valleys  approach  the  sea  they  will  be  sub- 
merged or  drowned. 


ALLUVIAL  CONES. 
Formed  at  the  foot  of  each  mountain  gully. 

These  drowned  river  valleys  form  some  of  the  finest 
harbors  on  the  coast.  San  Francisco  Bay,  Narragansett 
Bay  and  New  York  harbor  are  examples  of  protected 
harbors  due  to  the  submergence  of  rivers.  The  mouth 
of  the  Hudson  was  formerly  some  seventy  miles  to  the 
east  of  Long  Island,  that  of  the  St.  Lawrence  to  the  east 
of  Nova  Scotia.  In  fact  the  Atlantic  coast  north  of  the 


348  FIRST   YEAR   SCIENCE 

1  rf* 

Hudson   furnishes   innumerable   examples  of   submerged 
river  valleys. 

The  tributary  streams  which  enter  low'  down  on  a  river's 
course,  after  submergence  enter  the  sea  directly  in  the 
bays  formed  by  the  submerged  valley.  Such  rivers  may 
be  called  dismembered  rivers.  Thus  a  coast  region  which 
was  formerly  well  dissected  by  streams  will  on  submer- 


FAN  FILLED  VALLEY. 

» 

Notice  how  the  river  is  forced  to  wander  around  the  edges  of  the  fans. 

gence  become  penetrated  by  a  great  number  of  irregular 
channels  and  bays. 

Delaware  and  Chesapeake  bays,  where  the  early  settlers 
each  had  a  nice  little  sea  inlet  instead  of  a  rough  wagon 
road  as  his  means  of  communication  with  his  neighbors, 
are  fine  examples  of  submerged  river  systems.  These 
drowned  river  valleys  enabled  the  early  settlers  to  pene- 
trate easily  into  the  country,  and  determined  many  of  the 


ALLUVIAL   CONES  AND  FANS  349 

early  settlements,  like  Philadelphia,  New  York  and  Provi- 
dence. 

161.  Alluvial  Cones  and  Fans.  —  When  a  stream  having 
a  steep  grade  and  bearing  a  heavy  load  of  sediment 
emerges  upon  a  flat  country  where  the  grade  is  suddenly 
reduced,  it  so  quickly  deposits  its  sediment  as  to  be  con- 
tinually obstructing  its  own  course  and  forcing  itself  to 


LAKK  DKLTA. 
Notice  the  triangular  formation. 

find  new  channels.  It  thus  builds  a  fan  or  cone-shaped 
deposit  pointed  toward  the  place  where  the  stream  reached 
the  plain.  If  the  material  is  coarse,  the  deposit  will  have 
a  steep  slope ;  if  fine,  a  gentle  slope  resembling  a  spread- 
ing fan.  Sometimes  these  fans  so  overlap  each  other 
as  to  form  an  irregularly  sloping  plain. 

Plains  of  this  kind  are  found  along  the  base  of  many 
mountain  regions.     If  such  formations  occur  in  regions  of 


350  FIRST    YEAR   SCIENCE 

little  rainfall,  they  yield  themselves  with  peculiar  facility 
to  irrigation,  as  ditches  can  be  easily  led  out  from  the  apex 
of  the  cone  in  all  directions.  Southern  'California  offers 
many  examples  of  easy  irrigation  due  to  such  cones. 

162.  Deltas.  —  When  a  river  enters  a  body  of  quiet  water, 
its  current  is  gradually  checked  and  it  deposits  its  material 
in  somewhat  the  same  way  as  on  emerging  upon  a  flat 


CONE-SHAPED  DELTA  IN  LAKE  GENEVA. 

country.  But  here  the  deposition  is  more  gradual  and 
the  slope  of  the  deposited  material  less  steep.  The  sedi- 
ment, too,  is  sorted  by  the  water,  and  the  finer  material  is 
carried  far  out  from  the  river  mouth.  Formations  of  this 
kind  are  called  deltas,  from  the  Greek  capital  letter  Delta 
(A)  which  has  the  shape  of  a  triangle.  Few  deltas  have 
this  ideal  shape,  but  there  is  a  general  correspondence  to  it. 
If  the  delta-forming  stream  descends  steeply,  it  may 


DELTAS 


351 


build  a  delta  with  a  steep  upper  surface  rising  cone-shaped 
above  the  water.  Many  of  the  deltas  in  Lake  Geneva  are 
of  this  kind.  If  the  grade  is  slight,  the  delta  will  be  sim- 
ply a  continuation  of  the  flood  plain  of  the  river.  Such 
is  the  Mississippi  delta.  The  layers  of  sediment  compos- 


LAKE  BRIENZ,  FROM  ABOVE  INTERLAKEN. 

A  rapidly  eroding  stream  at  the  extreme  right  has  built  a  great  delta 
dividing  the  ancient  lake  into  two  parts. 

ing  the  delta,  slope  away  from  the  point  where  the  river 
enters  the  still  water.  Here,  as  in  the  alluvial  cone,  the 
river  is  continually  silting  up  its  outlet  and  being  forced 
to  seek  new  channels.  In  large  deltas  the  river  generally 
enters  the  sea  through  several  channels  or  distributaries, 
as  they  are  called.  This  is  seen  in  the  map  of  the  Missis- 
sippi delta  (page  352). 


352 


•FIRST   YEAR   SCIENCE 


Deltas  have  rich,  fine-textured  soils  and  are  very  fertile. 
The  Nile  delta  during  all  history  has  been  noted  for  its 
fertility.  But  they  are  treacherous  places',  as  they  are  liable 
to  inundations  by  the  overflowing  of  the  river  at  time  of 
flood.  Because  they  are  pushed  out  into  the  sea,  they 
are  peculiarly  exposed  to  the  sweep  of  the  waves  in  great 
storms. 


MOUTHS   OF   THE 

MISSISSIPPI    RIVER 


The  rate  at  which  deltas  grow  depends  upon  the  amount 
of  material  carried  by  the  river  and  upon  the  tides  and 
currents  at  its  point  of  outlet.  In  seas  where  the  currents 
and  tides  are  strong,  no  deltas  are  formed,  except  by  very 
large  streams  such  as  the  Yukon,  the  Hoang-Ho  and  the 
Ganges.  In  quiet  seas  deltas  are  readily  built.  The 
delta  of  the  Mississippi  is  more  than  200  miles  long  and 
has  an  area  of  more  than  12,000  square  miles.  The  Po  in 


HISTORY  AND  RIVERS  353 

historic  time  has  built  a  delta  more  than  14  miles  beyond 
Adria,  a  former  port  which  gave  its  name  to  the  Adriatic 
Sea. 

163.  History  and  Rivers.  —  From  earliest  times  rivers  have 
played  a  most  important  part  in  the  world's  history.  At 
first  almost  all  human  movement  was  along  river  valleys, 
as  they  offered  the  easiest  route  of  travel.  Here,  too,  men 
found  the  fertile  and  easily  worked  land  so  necessary  in 
their  primitive  agriculture.  Thus  their  settlements  were 
usually  placed  upon  the  banks  of  rivers.  In  war  the 
river  offered  a  means  of  defense,  as  the  Tiber  so  often  did 
to  Rome. 

Before  the  time  of  railways,  rivers  and  lakes  supplied 
almost  the  only  means  of  inland  commerce.  In  our  own 
country  the  hundred  and  fifty  miles  of  unobstructed  river- 
way  stretching  from  New  York  to  the  north  was  the  great 
road  from  Canada  and  the  Lakes  to  the  sea,  fought  for 
persistently  in  French  and  Indian  Wars  as  well  as  in  the 
Revolution.  If  in  the  Revolution  the  British  could  have 
obtained  control  of  the  Hudson,  they  would  have  effectu- 
ally separated  the  colonists  in  the  north  from  those  in  the 
south  and  would  probably  have  been  able  to  crush  each 
separately. 

The  Mississippi  River  served  for  years  as  the  only  artery 
of  transportation  from  the  interior  of  the  country  to  the 
sea.  When  Spain  held  the  mouth  of  this  river  and  Con- 
gress was  unable  or  unwilling  to  exert  itself  to  obtain 
the  privilege  for  American  boats  to  pass  to  the  sea,  it 
seemed  for  a  time  that  the  sturdy  colonists  along  the  Ohio 
and  Mississippi  would  either  form  an  independent  country 
and  fight  for  the  privilege  or  else  in  some  way  ally  them- 
selves with  Spain,  so  vital  to  them  was  the  need  of  this 
waterway.  In  the  Civil  War  vast  amounts  of  blood  and 
treasure  were  spent  in  fighting  for  the  control  of  this  river. 


354  FIRST   YEAR   SCIENCE 

These  are  but  a  few  examples  taken  from  our  own 
history  of  the  importance  of  rivers.  They  could  be  dupli- 
cated in  almost  every  country  of  the  glooe. 

164.  Great  Rivers  of  the  United  States.  —  There  are  four 
great  river  basins  wholly  or  partly  within  the  United 
States:  the  St.  Lawrence,  the  Mississippi,  the  Columbia 
and  the  Colorado.  The  first  two  of  these  are  navigable 
for  great  distances  and  furnish  unexcelled  interior  water- 


DRAINAGE  BASINS  OF  THE  UNITED  STATES. 
Notice  the  positions  of  the  divides  separating  the  different  drainage  areas. 

ways.  Notwithstanding  the  great  development  of  rail- 
ways they  still  exert  a  vast  influence  upon  the  commerce 
of  the  country. 

The  fit.  Lawrence  River  with  the  Great  Lakes,  which 
are  geographically  a  part  of  it,  is  the  greatest  internal 
waterway  in  the  world.  From  the  head  of  Lake  Superior 
to  the  mouth  of  the  St.  Lawrence,  a  distance  of  about 
2400  miles,  by  aid  of  the  canals  which  have  been  built 
around  the  rapids  and  falls,  vessels  of  14  feet  draft  can 


GREAT  RIVERS   OF  THE    UNITED   STATES 


355 


pass  to  the  sea.  More  tonnage  passes  through  the  "  Soo  " 
canal  between  Lake  Superior  and  Lake  Huron  than  passes 
through  the  Suez  canal.  Here  pass  the  greatest  fleets 
bearing  wheat,  iron,  and  lumber  that  the  world  has  ever 
seen. 

The  old  river  which  once  drained  this  region  passed 
through   various   vicissitudes    before    the    present   noble 


THE  "  Soo  "  CANAL  AT  SAULT  STE.  MARIE. 
Notice  the  "  whale-backs,"  a  type  of  boat  peculiar  to  the  $reat  Lakes. 

waterway  was  formed.  From  Montreal  to  the  sea  it  has 
been  drowned  by  a  depression  of  the  land.  Its  upper 
basin  has  been  enlarged  in  places  by  the  action  of  the 
glacial  ice,  and  in  other  places  it  has  been  dammed,  thus 
causing  lakes  and  falls. 

The  Mississippi  and  its  tributaries  offer  navigable  water- 
ways of  about  9000  miles.  It  is  the  greatest  navigable 
river  system  in  the  world.  From  the  Rocky  Mountains 


356 


FIRST   YEAE   SCIENCE 


on  the  west  to  the  Appalachians  on  the  east  and  from  the 
northern  border  of  the  country  to  the  Gulf,  the  spread- 
ing arms  of  its  tributaries  stretch  out  ready  to  bear  to  the 


THE  JETTIES  OF  THE  MISSISSIPPI. 

To  keep  the  river  from  silting  up  its  channel,  it  is  confined  between 
jetties  and  made  to  flow  swiftly. 

ocean  by  cheap  and  easy  paths  the  products  of  this  vast 
interior  basin.  By  the  aid  of  the  Panama  canal  these 
varied  products  may  travel  directly  by  water  without 
more  than  one  or  two  re-shipments  from  their  source  in 


DELTA  LAND  OF  THE  LOWER  MISSISSIPPI. 

the  vast  continental  interior  to  the  uttermost  parts  of  the 
earth. 

This   noble   river  presents   in  its   eventful  history   an 


GEE  AT  RIVERS   OF  THE   UNITED   STATES         357 

epitome  of  the  geographical  history  of  our  continent.  It 
winds  its  masterful  way  over  the  oldest  and  youngest 
rocks.  For  part  of  its  course  it  follows  a  valley  built  long 
before  the  Glacial  Period  shrouded  the  northern  part  of 
the  continent  in  ice.  In  the  northern  part  of  its  course 
the  blanket  of  debris  left  by  this  vanished  ice  choked  its 
path  arid  forced  it  to  seek  a  new  channel.  For  the  south- 


THE  COLUMBIA  RIVER  AND  ITS  OLD  FLOOD  PLAIN. 

ern  part  of  its  course  its  mighty  sediment-laden  waters 
built  new  lands  that  it  might  extend  its  dominion. 

At  times  in  its  history  its  might  has  been  greater  than 
now  and  at  times  less.  But  through  all  its  history  it  has 
borne  to  the  ocean  the  ceaseless  current  flowing  from  the 
heart  of  our  continent.  To  it  the  modern  geographer 
turns  again  and  again  as  an  inexhaustible  record  of  geo- 
graphical development.  The  geographical,  political,  in- 
dustrial and  commercial  history  of  this  continent  are 
closely  connected  with  this,  its  mightiest  artery. 


358  FIRST   TEAR  SCIENCE 

The  Columbia  River,  although  navigable  for  a  distance 
of  only  500  or  600  miles,  and  thus  never  destined  to  have 
the  commercial  importance  of  the  St.  Lawrence  and  the 
Mississippi,  presents  features  of  great  interest.  Guided 
by  this  stream  the  first  settlers  found  their  way  to 
our  northwest  territory.  Along  its  depressed  mouth  the 
rich  and  prosperous  states  of  Washington  and  Oregon 
were  nurtured  through  their  infancy.  Over  its  possession 
Englishman  and  American  long  contended. 

This  contention  of  man,  however,  was  but  an  echo  of 
the  long  contention  of  the  river  itself  to  hold  its  course. 
Flowing  in  a  region  of  growing  mountains,  it  was  forced 
again  and  again  to  cut  its  way  through  barriers  uplifted 
across  its  path.  Sometimes  for  a  time  it  was  checked  and 
forced  to  raise  itself  into  a  lake  in  order  to  surmount  the 
obstruction  placed  in  its  way.  but  its  strength  never  failed, 
and  so  through  new-born  ridges,  through  lake  beds  born 
of  its  own  struggle,  through  growing  depressions  filled  by 
its  own  labor,  it  held  its  course  steadfastly  to  the  sea.  For 
part  of  its  way  it  flows  through  canonlike  valleys,  and  its 
main  tributary,  the  Snake,  has  built  for  itself  through  great 
beds  of  horizontal  igneous  rocks  a  canon  but  little  inferior 
to  that  of  the  Colorado. 

The  fourth  great  river,  the  Colorado,  has  industrially 
and  commercially  attained  but  little  usefulness.  Al- 
though navigable  to  about  400  miles  from  its  mouth  there 
is  little  need  in  the  country  it  traverses  for  transportation 
in  the  direction  of  its  course.  But  what  it  lacks  in  utility, 
it  makes  up  in  sceneiy.  To  no  river  on  the  face  of  the 
earth  has  the  opportunity  been  given  to  show  its  sculptur- 
ing power  as  to  the  Colorado. 

Flowing  as  it  does  through  an  arid  region  of  nearly 
horizontal  rocks,  it  has  carved  a  giant  trough  for  itself, 
leaving  upon  the  lofty  sides  the  uneffaced  chisel  marks  of 


GREAT  RIVERS   OF  THE   UNITED   STATES         359 

all  its  erosive  helpers.  The  rill,  the  rivulet,  the  intermit- 
tent torrent,  the  sand  blast  of  the  scouring  wind,  the  pull 
of  gravity,  the  varied  resistances  of  the  rock  layers,  the 
structure  and  composition  of  these  layers  have  each  and 
all  left  their  peculiar  impress  upon  the  resulting  sculpture. 
Standing  beside  this  mighty  chasm,  one  is  impressed,  as  no- 
where else,  with  the  mighty  power  of  erosive  agents. 


THE  COLORADO  RIVKR. 
Flowing  through  a  deep-cut,  narrow  valley. 

And  yet  here  is  seen  only  the  beginning  of  the  vast 
work  which  these  forces  have  before  them.  They  have 
built  only  the  narrow  trough  of  what  must  be  developed 
into  a  wide  and  gently  sloping  valley,  and  have  hewn  out 
here  and  there  a  ravine  in  that  great  upland  which  in 
time  they  must  carve  into  the  mature  forms  of  a  thoroughly 
dissected  country.  If  the  region  had  not  been  so  dry,  the 


360  -FIRST   YgAR   SCIENCE 

work  of  dissection  would  have  progressed  much  farther 
before  the  river  had  been  able  to  sink  its  channel  so 
deep.  The  water  that  falls  hundreds  of  miles  away  is 
doing  a  mighty  work  which  the  meager  rainfall  of  the 
region  through  which  it  passes  cannot  supplement. 
Majestic,  awe-inspiring,  stupendous,  this  gigantic  trench 
is  but  a  prank  of  the  river's  boisterous  youth. 

Summary.  —  Just  as  the  waves  and  ocean  currents  work 
upon  the  coastlines,  so  the  rain  and  the  streams  are  con- 
stantly wearing  down  the  surface  of  the  land.  All  streams 
come  from  rain  or  melting  snow,  which  condenses  in  the 
air  after  evaporating  from  water  surfaces.  The  rainfall 
varies  from  nothing  at  all  in  some  places  to  over  fifty  feet 
a  year  in  others,  but  in  the  United  States  the  greatest 
rainfall  is  about  eighty  inches  a  year. 

Some  of  the  rain  evaporates  at  once  after  falling ;  some 
flows  away  on  the  surface  of  the  land  ;  some  sinks  into  the 
ground,  to  return  as  springs,  wells  and  geysers.  The 
water  which  flows  along  the  surface  has  the  greatest  effect 
upon  the  land.  It  forms  the  little  streams  which  remove 
the  surface  water,  the  huge  rivers  which  drain  the  country 
and  form  great  arteries  of  trade,  and  the  beautiful  lake- 
reservoirs  which  hold  back  floods  and  offer  easy  trans- 
portation to  mighty  ships. 

But  most  important  of  all  is  the  erosion  caused  by  flow- 
ing water.  It  wears  down  the  hills  and  spreads  them  out 
in  fertile  fields,  in  deep  trenches  and  broad  valleys ;  it  fills 
lakes  and  builds  great  deltas.  By  its  falls  and  rapids  it 
furnishes  water  power  for  manufactures. 

Rivers  that  have  not  yet  widened  their  valleys  and  still 
have  falls  and  rapids  are  called  young  ;  an  old  river  is  one 
whose  bed  has  been  worn  smooth,  and  which  has  built 
for'  itself  a  broad  level  valley,  through  which  it  wanders, 


SUMMARY  361 

doing  little  if  any  erosive  work.  Rivers  sometimes  de- 
velop flood  plains  through  which  they  wander  in  S-shaped 
meanders.  Sometimes  a  river  cuts  back  its  divide  so  far 
that  it  reaches  another  river,  thus  diverting  another 
stream  through  its  channel. 

If  the  region  of  a  river  becomes  elevated,  the  river  may 
be  revived,  and  if  it  is  an  old  river  with  meanders,  in- 
trenched meanders  may  be  formed.  Sometimes  the  eleva- 
tion of  the  land  causes  a  river  to  be  laked  or  reversed  ;  if 
it  maintains  its  previous  course  in  spite  of  the  elevation, 
it  is  called  antecedent. 

If  a  river  region  becomes  depressed,  the  river  may  be 
drowned  and  its  branches  may  enter  the  sea  separately  as 
dismembered  rivers.  Many  rivers  build  deltas  where  they 
empty  into  still  bodies  of  water  and  when  the  slope  is 
steep,  they  may  form  fans. 

Rivers  have  always  played  a  great  part  in  history,  from 
the  time  Egypt  was  first  called  the  "  Gift  of  the  Nile  "  to 
the  influence  of  the  Mississippi  and  St.  Lawrence  on  the 
settlement  and  development  of  the  United  States. 


QUESTIONS 

What  conditions  influence  the  amount  of  rainfall  of  a  place? 

What  determines  what  will  become  of  the  rainfall  when  it  falls 
upon  the  ground  ? 

What  does  the  water  do  which  sinks  into  the  ground? 

Where  are  geysers  found?     What  are  they  ? 

Trace  the  probable  journey  of  the  water  that  fell  near  your  home 
during  the  last  heavy  rain  until  it  reaches  its  journey's  end. 

What  determines  whether  a  lake  is  fresh  or  salt  ?  What  are  the 
great  benefits  derived  from  lakes  ? 

Describe  some  effects  of  running  water  that  you  have  seen. 

Why  does  not  all  the  water  that  fell  in  your  town  during  a  heavy 
rain  flow  by  your  home  ?  Where  is  the  «  divide  '  ? 

What  are  some  of  the  causes  which  have  formed  falls  and  rapids? 


362  FIRST   YEAR   SCIENCE 

7   .  ,r* 

Describe  the  life  history  of  a  river. 
What  peculiarities  have  rivers  of  dry  climates? 
Describe  some  of  the  accidents  which  are  liable  to  happen  during 
a  river's  history. 

How  are  alluvial  cones  and  fans  formed? 
Where  and  how  do  rivers  build  deltas  ? 
What  have  been  the  effects  of  rivers  upon  history  ? 
Describe  the  four  great  rivers  of  the  United  States. 


CHAPTER   XI 
ICE  AND  WIND  SOULPTUKES 

165.  Snow  in  Winter.  —  When  the  temperature  of  the  air 
falls  below  the  freezing  point,  its  moisture  congeals  into 
little  flake-like  crystals  and  falls  as  snow.      Where  the 
cold  is  continuous  for  a  con- 
siderable time,  the  snow  may 

accumulate  in  deep  layers  over 

the  ground.     If  the  heat    of 

the  summer  is  not  sufficient 

to  melt  all   the    snow   which 

falls  in  the  winter,  then  the  layers  of  snow  will  increase 

from  year  to  year. 

To  have  this  occur  the  temperature  for  the  whole  year 
need  not  be  below  the  freezing  point,  but  the  heat  of  the 
summer  must  not  be  sufficient  to  melt  the  snow  which  fell 
in  the  colder  season.  Lofty  mountains,  even  in  the  trop- 
ics, have  their  upper  parts  snow-covered.  In  the  far  north 
and  the  far  south  the  line  of  perpetual  snow  falls  to  sea 
level,  inclosing  the  mighty  expanse  of  the  Arctic  and  the 
Antarctic  snow  fields. 

166.  Glaciers.  —  Wherever  there  is  not  enough  heat  in 
the  warm  season  to  melt  the  snow  which  accumulates  dur- 
ing the  cold  season,  a  thick  covering  of  snow  and  ice  will 
in  time  be  formed.     The  ice  is  due  to  the  pressure  exerted 
on  the  lower  layers  by  the  weight  of  the  snow  above  and 
to  the  freezing  of  the  percolating  water  which  come"s  from 
the  summer  melting  of  the  upper  snow  layers. 

Although  ice  in  small  pieces  is  brittle,  in  great  masses 

363 


364  -FIRST  YEAR   SCIENCE 

it  acts  somewhat  like  a  thick  and  viscid  liquid.  It  con- 
forms itself  to  the  surface  upon  which  it  lies,  and  under 
the  pull  of  gravity  or  pressure  from  an  accumulating  mass 
behind,  slowly  moves  forward,  resembling  in  some  ways 
thick  tar  creeping  down  an  incline  or  spreading  out  when 
heaped  into  a  pile.  The  exact  manner  of  glacial  move- 
ment, however,  is  not  fully  understood. 


SNOW   FlKLD   AT   THE   HEAD   OF   A   GLACIER. 

In  mountain  regions  where  the  snow  holds  over  through 
the  summer,  the  wind-drifts  and  the  snow-slides  carry 
great  quantities  of  snow  into  the  upper  valleys,  until  ever 
accumulating  masses  of  snow  and  ice,  hundreds  of  feet 
thick,  are  formed.  The  ice  then  slowly  flows  down  a  val- 
ley till  a  point  is  reached  where  the  melting  at  the  end  is 
equal  to  the  forward  movement.  An  ice  stream  of  this 


GLACIERS 


365 


kind  is  called  a  valley  glacier  or  an  Alpine  glacier,  because 
first  studied  in  the  Alps. 


THE  GORNER  GLACIER. 
A  typical  Alpine  Glacier. 

Although  the  moving  ice  conforms  to  the  bed  over 
which  it  passes,  it  does 
not  yield  itself  to  the 
irregularities  as  easily  as 
does  water.  When  it 
passes  through  a  narrows 
or  over  a  steep  and  rough 
descent,  it  is  broken  into 
long,  deep  cracks  called 
crevasses.  These  make 
travel  along  glaciers 
sometimes  very  danger- 
ous. The  travelers  are 
usually  tied  together  with  ropes,  so  that  if  one  of  the 


CREVASSES  IN  A  GLACIER. 
The  danger  points  in  travel  over  glaciers. 


366 


FlflST   YEjlR   SCIENCE 


party  slips  into  a  crevasse,  the  others  will  be  able  to  hold 
him  up  and  pull  him  out. 

A  glacier,  like  a  river,  is  found  to  flow  fastest  near  the 
middle  and  on  top,  and  slowest  at  the  bottom  and  on  the 
sides.  The  rate  of  motion  in  the  Alpine  glaciers  varies 
generally  somewhere  between  50  feet  and  one  third  of  a 


THE  COE  GLACIER,  MOUNT  HOOD. 

mile  in  a  year,  being  greatest  in  the  summer  and  least  in 
the  winter. 

Alpine  glaciers  are  found  not  only,  as  the  name  would 
indicate,  in  the  Alps,  but  also  in  Norway,  in  the  Himalayas, 
among  the  higher  mountains  in  the  western  United  States, 
on  Mt.  Shasta  and  in  fact  wherever  the  snow  accumulates 
in  the  mountain  valleys  year  after  year. 

As  glaciers  creep  down  the  valleys,  dirt  and  rocks  fall 
upon  their  edges  from  the  upper  valley  sides  and  are 
borne  along  upon  the  ice.  If  two  glaciers  unite  to  form  a 
larger  one,  the  debris  upon  the  two  sides  which  come  to- 


GLA  CIERS 


367 


gether  forms  a  layer  oi|  dirt  and  rocks  along  the  middle  of 
the  larger  glacier.  At  the  end  of  the  glacier  this  mate- 
rial which  it  has  borne  along  is  deposited  in  irregular 
piles  of  rocks  and  dirt. 

The  accumulations  of  debris  along  the  sides  are  called 
lateral  moraines,  those  in  the  middle,  medial  moraines,  and 
those  at  the  end,  terminal  moraines.  Great  bowlders  may 


THE  DANA  GLACIER  IN  THE  HIGH  SIERRAS. 

be  carried  along  on  the  ice  for  long  distances  without  the 
edges  being  worn,  since  they  are  carried  bodily  and  not 
rolled  as  in  streams. 

On  the  under  surface  of  the  glacier,  rocks  are  dragged 
along  firmly  frozen  into  the  ice.  The  weight  of  the  gla- 
cier above  presses  them  with  tremendous  force  upon  the  sur- 
face over  which  the  glacier  passes.  In  this  way  scratches 
or  grooves  are  made  in  the  bed  rock  underlying  the  gla- 


368 


\FIRST   YEAR   SCIENCE 


cier,  as  well  as  upon  the  bowlders  themselves.     Scratches 
of  this  kind  are  called  glacial  scratches  or  strice.     They, 
are  found  abundantly  in  places  that  have  been  glaciated. 
The  rubbing  of  the  rocks   upon   each   other  wears  them 

away  and  grinds  them 
into  fine  powder  called 
glacial  flour,  which  gives 
a  milky  color  to  the 
streams  flowing  from 
glaciers. 

If  a  glacier  extends 
over  a  region  where  the 
surface  has  been  weath- 
ered into  soil,  this  fine 
material  may  be  shoved 
along  under  the  ice  for 
great  distances.  When 
a  glacier  melts,  all  the 
material  which  it  has 
moved  along  under  it, 
as  well  as  that  which  it 
has  carried  on  its  sur- 
face or  frozen  into  it,  is  deposited,  forming  what  is  called 
ground  moraine.  This  is  the  formation  which  constitutes 
the  soil  of  many  of  our  northern  states. 

The  melting  of  glacial  ice,  whether  by  the  sun's  heat  on 
top,  by  friction  on  the  bottom  or  from  whatever  cause, 
produces  streams  which  flow  in  the  ice-cut  channels  under 
the  glacier  and  emerge  in  front,  laden  with  rock,  glacial 
flour,  and  silt.  Where  the  amount  of  material  these 
streams  carry  is  great,  it  is  usually  deposited  in  an  al- 
luvial plain  near  the  end  of  the  glacier. 

The  length  of  a  glacier  does  not  always  remain  the 
same,  but  increases  and  decreases  slowly  in  conformity 


THE  FIESCH  GLACIER. 
Notice  the  medial  moraine. 


GLACIERS 


with  the  amount  of  snow  which  falls  in  successive  years. 
Like    rivers,   only  more  slowly,  they  are  subject  to  the 


A  TERMINAL  MORAINE. 
changing  conditions  of  atmospheric  precipitation. 

Wherever  glaciers  are  easily  approached  they  form  a 
great  attraction  for  the 
summer  tourist.  The 
glistening  white  snow 
fields  circled  by  the 
green  foliage  of  the 
lower  slopes,  with  the 
glaciers  descending  in 
long,  white  arms  down 
the  valleys,  pouring  out 
turbulent,  milky-colored 
streams  from  their  lower 
ends,  and  here  and  there 
covered  with  bowlders 


A  BOWLDER  BORNE  ALONG  ON  TOP 

OF  A  GLACIER. 
Notice  its  size  as  compared  to  the  umbrella. 


and  long,  dark  lines  of  medial  moraines,  form  a  picture 


370 


FIRST   YEAR   SCIENCE 

' 


which  once  seen  is  never  forgotten,  and  the  enticement  of 
which  lures  the  traveler  again  and  again  to  revisit  the 


A  STONE  SCRATCHED  BY  A  GLACIER. 

fascinating  scene.     The  exhilaration  of  a  climb  over  the 
pathless  ice  with  the  bright  summer  sun  shining  upon  it, 

the  bracing  air,  and  the 
ever  changing  novelty 
of  the  surroundings 
make  a  summer  among 
the  glaciers  almost  like 
a  visit  to  a  land  of  en- 
chantment. 

For  this  reason  Switz- 

erland  has  become  the 
summer  playground  of 


ROCKS    POLISHED    BY    A   GLACIER. 


The  glacier  in  the  background  recently 
extended  down  over  these  rocks. 


Europe  and  America, 
and  there  the  tourist 
crop  is  the  best  crop  that 
the  natives  raise,  and  the  scenery  is  more  productive  than 
the  soil.  Norway,  with  the  additional  beauty  of  its  fiords, 
is  fast  becoming  another  Mecca  of  the  tourist,  and  this 


ICE  FIELDS 


371 


region,  denuded  and  made  barren  by  the  ancient  glaciers, 
is  now  becoming  rich  and  prosperous  because  of  the  glacial 
remnants  still  left.  The  high  Sierras  are  each  year  entic- 
ing greater  and  greater  numbers  of  travelers  to  enjoy  their 
wonderful  beauties  arid  their  invigorating  climate. 


MOUNT  HOOD. 

A  view  taken  in  the  fall  when  the  mountain  is  covered  with  snow,  although 
the  surrounding  country  is  still  green. 

167.  Greenland  and  the  Antarctic  Ice  Fields.  —  The  whole 
of  the  island  of  Greenland  is  covered  with  a  deep  sheet  of 
ice  except  a  narrow  border  along  a  portion  of  the  coast 
and  the  part  of  the  island  north  of  82°,  which  has  little 
precipitation.  The  extent  of  the  ice  sheet  is  nearly  equal 
to  the  area  of  all  the  states  of  the  United  States  east  of 
the  Mississippi  and  north  of  the  Ohio.  The  depth  of  the 
ice  is  not  known,  but  probably  in  some  places  is  at  least 
several  thousand  feet.  Although  along  the  coast  moun- 
tains rising  from  5000  to  8000  feet  are  not  uncommon, 
yet  in  the  interior  the  thickness  of  the  ice  is  so  great  that 
no  peaks  rise  above  it. 


372  FIRST   YEAR   SCIENCE 

'       .  V* 

The  surface  of  the  inland  ice  is  a  smooth  snow  plain. 
Extending  from  this  ice  field  are  huge  glaciers  having  at 
their  ends  a  thickness  of  from  1000  to  2000  feet.  One  of 
these  has  a  rate  of  motion  of  nearly  100  feet  per  day  in 
summer,  the  highest  rate  ever  observed  in  a  glacier.  The 
average  movement  throughout  the  year  on  the  border  of 
the  ice  sheet  is  probably  not  more  than  two  inches  a  day. 


A   VIEW   OF   THE   JUNGFRAU. 

Showing  the  snowy  mountains  and  verdant  valleys  which  make 
Switzerland  the  delight  of  the  tourist. 

In  the  Antarctic  region  an  area  vastly  greater  than' 
Greenland  is  covered  with  ice  probably  of  a  greater  thick- 
ness. Although  little  is  known  about  this  ice  cap,  it  is 
thought  by  some  explorers  to  be  nearly  as  large  as  Europe 
and  to  rest  partly  on  an  Antarctic  continent  and  partly 
on  the  sea  bottom. 

168.  Icebergs.  —  Experiment  129.  —  Fill  a  beaker  so  full  of  ice 
water  that  if  any  more  is  added  it  will  run  over.  Put  carefully  into 


ICEBERGS 


373 


the  beaker  a  piece  of  ice,  and  catch  in  another  beaker  the  water 
which  runs  out.  After  all  the  water  which  readily  overflows  has 
been  caught  in  the  second  beaker,  carefully  push  the  ice  into  the 
water  till  it  is  entirely  submerged,  and  catch  in  a  third  beaker  the 
water  which  overflows.  The  experiment  must  be  done  with  consid- 
erable quickness,  so  that  the  ice  will  not  melt  between  the  two 
steps. 

The  water  in  the  second  beaker  is  equal  to  the  volume  of  the  ice 
submerged  when  it  floats,  and  that  in  the  third  beaker  to  the  volume 


AN  ICEBERG. 

of  the  part  out  of  water  when  the  ice  floated.  The  two  together  are 
equal  to  the  whole  volume  of  the  ice.  Measure  in  a  graduate  or 
weigh  on  a  balance  these  two  volumes  of  water.  (A  cubic  centi- 
meter of  water  weighs  a  gram.)  Determine  the  part  of  a  floating 
block  of  ice  that  is  out  of  water.  Would  the  amount  of  ice  out  of 
water  be  greater  or  less  if  the  water  were  salt?  This  can  be  demon- 
strated by  dissolving  a  considerable  quantity  of  salt  in  the  ice  water 
and  very  rapidly  repeating  the  experiment. 

When  a  glacier  extends  out  into  the  sea,  the  water  tends 
to  float  the  ice.  If  it  extends  out  into  deep  enough  water, 
the  buoyancy  of  the  water  will  be  sufficient  to  crack  the  ice, 


874  FIRST  YEAR   SCIENCE 

and  the  end  of  the  glacier  will  float  off  as  an  iceberg. 
Glacial  ice  is  about  eight  ninths  under  water  when  it  floats. 
Icebergs  may  float  for  long  distances  before  they 
melt.  In  the  North  Atlantic  the  steamer  routes  are 
changed  in  the  summer  months  for  fear  of  running  into 
floating  bergs.  Some  of  the  most  appalling  disasters  of 
the  sea  have  been  due  to  ships  colliding  with  icebergs. 
As  the  berg  melts,  the  rocks  and  gravel  or  whatever  it 


BOWLDERS  AND  SAND  LEFT  BY  A  ESTREATING  GLACIER. 

may  have  upon  it  drop  into  the  sea,  so  that  the  waste 
brought  down  to  the  sea  by  the  glacier  may  be  spread  over 
the  sea  bottom  far  away  from  the  place  where  it  origi- 
nated. Much  of  the  knowledge  of  the  geology  of  the 
Antarctic  continent  has  been  gained  from  the  bowlders 
dredged  up  at  sea. 

Although  icebergs  in  the  northern  seas  are  sometimes 
very  large,  those  in  the  Antarctic  region  are  vastly  larger. 
They  have  been  seen  extending  above  the  water  200  or 


GLACIAL   FORMATIONS  375 

more  feet  with  broad  flat  tops  miles  in  length.     They 
were  indeed  huge  floating  islands  of  ice. 

169.  Glacial  Formations.  —  In  a  region  which  has  been 
glaciated,  peculiar  deposits  are  found  which  occur  nowhere 
else.  Sometimes  the  end  of  a  glacier  remains  compara- 
tively stationary  over  an  area  for  a  considerable  time, 
owing  to  the  advance  of  the  ice  being  just  balanced  by 


A  DRUM  LIN. 

These  low,  smooth,  rounded  hills,  like  that  seen  in  the  background, 
usually  extend  north  and  south. 

the  melting.  In  this  case,  the  morainic  material  which 
has  collected  on  the  top  is  deposited  over  the  surface, 
forming  irregular  heaps  of  bowlders,  gravel  and  sand,  with 
inclosed  hollows  between.  This  material  is  unstratified 
and  without  any  uniformity  in  its  arrangement. 

When  the  glacier  has  retreated,  ponds  and  lakes  are 
formed  in  the  depressions,  and  streams  wander  about  in 
the  low  places  between  the  heaps  and  receive  the  overflow 
of  some  of  the  lakes  and  ponds.  Others  of  these  lakes  and 
ponds  are  so  fully  inclosed  and  receive  the  drainage  from 
so  small  a  surface  that  not  enough  water  enters  to  over- 
flow the  rim.  The  arrangement  of  the  streams  is  unsym- 


376  .FIRST   YEAR   SCIENCE 

metrical  and  without  order.  The  whole  surface  is  a 
hodgepodge  of  glacially  dumped  material,  a  terminal 
moraine  country. 

Further  back  from  this  morainic  dumping  ground  may 
be  found  other  kinds  of  glacially  deposited  material.  If 
a  glacier  is  pushing  along  under  it  a  mass  of  material  and 
it  meets  some  obstruction,  or  if  on  account  of  melting  or 
a  decrease  in  the  rate  of  its  flow  it  has  not  the  power  to 
carry  its  load,  it  deposits  a  part  of  it.  The  ice  slides  over 


AN  ESKER. 

the  deposited  material  and  rounds  it  off,  but  leaves  it  as  a 
river  leaves  its  sand  bars. 

But  this  material  is  not  stratified,  like  the  material  left 
in  water.  When  the  glacier  melts  away,  these  rounded 
deposition  heaps  are  left  as  hills  of  greater  or  less  height. 
Since  the  material  forming  them  has  been  continually 
brought  from  the  direction  from  which  the  ice  came,  they 
will  have  their  greatest  extension  in  that  direction.  Such 
hills  have  received  the  name  drumlins. 

Where  there  are  stream  channels  in  the  under  surface 
of  the  ice,  the  streams  may  aggrade  or  fill  up  their  beds 


GLACIAL   FORMATIONS 


377 


as  rivers  do  when  overloaded.  When  the  glaciers  retreat, 
ice  walls  which  bordered  the  channels  melt  away,  and  the 
sand  and  gravel  which  the  streams  had  laid  down  along 
their  beds  are  left  as  long,  irregular  ridges,  at  the  end  of 
which  sometimes  an  alluvial  fan  or  delta  may  be  found. 
Such  long  ridges  are  called  eskers. 


GLACIAL  ROCK  LAKE. 

Where  the  glacier  has  little  load,  as  near  its  source,  the 
bed  rock  is  stripped  bare,  smoothed,  polished,  and 
scratched  by  the  material  which  the  ice  has  scraped  over 
it  and  borne  away.  Where  the  rock  is  soft,  it  is  scooped 
out,  and  hollows  are  formed,  afterward  making  lakes  ; 
and  where  it  is  hard,  rounded  ridges  are  made. 

The  valleys  through  which  glaciers  go  are  rounded 
out  and  left  shaped  like  a  V.  If  side  glaciers  join  the  main 
glacier,  they  may  not  be  able  to  wear  down  their  valleys 
as  fast  as  the  main  glacier,  so  the  mouths  of  these  V-shaped 


378 


FIRST   TJEAR   SCIENCE 


valleys  may  be  much  higher  than  the  bottom  of  the  main 
valley.     These  are  called  hanging  valleys.     (See  §  44.) 


A  V-SHAPED  VALLEY  IN  NORWAY. 

This  has  been  rounded  out  by  glaciers.    The  moisture  in  the  atmos- 
phere makes  it  necessary  to  hang  the  hay  up  to  dry,  as  seen  in 
this  picture. 

The  bowlders  which  are  borne  along  by  the  ice  are 
deposited  irregularly  over  the  surface  in  all  kinds  of  posi- 
tions when  the  ice  melts.  Some  of  them  are  very  large 
and  are  left  perched  high  up  on  the  hillsides  where  no 


GLACIATED  AEEAS 


379 


other  known  force  besides  moving  ice  could  have  carried 
them.  These  irregularly  distributed  perched  bowlders 
are  called  erratics. 

170.  Glaciated  Areas.  —  Over  large  areas  of  what  are 
now  the  most  thickly  populated  regions  of  North  America 
and  Europe  are  found 
widespread  formations 
similar  to  those  de- 
scribed in  the  preceding 
paragraphs.  The  soil 
throughout  is  not  like 
that  of  the  underlying 
rock  ;  it  must  have  been 
transported.  Careful 
examination  of  all  the 
surface  formations  has 
led  geologists  to  believe 
that  at  a  former  period 
in  the  earth's  •  history, 
perhaps  not  more  than 
a  few  thousand  years 
ago,  the  northern  part 
both  of  North  America 
and  Europe  was  covered 
with  a  thick  layer  of  ice,  which  after  several  advances  and 
retreats  finally  disappeared,  leaving  the  country  as  we  now 
find  it. 

Although  the  border  to  which  the  ice  extended  and 
many  of  the  changes  which  the  ice  made  in  the  surface  of 
the  country  have  been  carefully  studied  and  mapped,  yet 
the  cause  of  this  extension  of  the  ice  and  the  exact  time 
at  which  it  occurred  have  not  yet  been  determined.  Many 
theories  have  been  brought  forward  to  account  for  it,  but 
none  of  them  explains  all  the  facts. 


A  HANGING  VALLEY. 


380 


.FIRST   YEAR   SCIENCE 


That  the  ice  was  here  seems  to  be  sure,  but  exactly 
when  or  why  is  unknown.  This  period  when  the  ice  was 
of  great  extent  is  called  the  Glacial  Period.  Probabty  dur- 
ing the  earth's  history  there  have  been  several  of  these 

periods,  but  to  the  last 
is  due  the  great  changes 
wrought  upon  the  pres- 
ent  surface  of  the 
country  and  upon  its 
plants  and  animals. 

171.  Glacial  Lakes.  — 
In  northern  countries 
are  found  ponds  and 
lakes  filling  the  irregu- 
lar depressions  in  the 
deposit  left  by  the  re- 
treating ice.  Lakes  of 
another  kind  are  also 
sometimes  formed  in 
glaciated  regions.  The 
advancing  ov-  -etreating 
ice  may  happen  to  make 
a  barrier  to  the  escape 
of  the  drainage,  and  thus  may  form  a  lake  with  an  ice  dam 
at  one  end.  The  lake  will  continue  to  exist  only  as  long 
as  the  ice  obstructs  the  drainage. 

The  Marjelen  Lake  in  Switzerland  is  a  well-known  ex- 
ample of  this.  The  Aletsch  glacier,  the  greatest  of  all  the 
Swiss  glaciers,  obstructs  a  lateral  valley,  forming  an  ice 
wall  about  150  feet  in  height,  behind  which  the  drainage  of 
the  side  valley  accumulates  and  forms  a  lake.  Pieces  of 
ice  from  the  glacier  fall  off  into  it,  forming  icebergs  which 
float  upon  its  surface. 

Sometimes  a  crevasse  opens  in  the  ice  wall,  and  then  the 


A  HUGK  PKRCHKD  BOWLDER. 


GLACIAL  LAKES 


381 


lake  quickly  drains  and  floods  the  valley  at  the  end  of  the 
glacier.  This  formerly  caused  so  much  damage  that  a 
canal  has  been  constructed  across  the  head  of  the  valley, 
so  that  now  no  great  quantity  of  water  can  accumulate 
behind  the  ice  dam.  When  the  lake  drains,  the  bottom  is 
left  as  a  comparatively  level,  dry  plain  until  the  crevasse 
closes  and  the  lake  again  forms. 


MARJELEN  LAKE. 

Toward  the  close  of  the  Glacial  Period  a  vast  lake  of 
this  kind  was  formed  in  the  northern  part  of  the  United 
States,  the  region  now  drained  by  the  Red  River  of  the 
North.  The  slope  of  the  land  is  here  toward  the  north, 
and  as  the  ice  retreated  it  formed  a  barrier  to  the  drain- 
age and  dammed  back  a  great  sheet  of  water  in  front  of 
it.  When  the  ice  melted,  the  lake  was  drained,  leaving 
the  flat  fertile  plain  through  which  the  Red  River  now 
flows.  The  ancient  glacial  lake  has  received  the  name  of 


382 


FIRST   TEAR   SCIENCE 

V* 


Lake  Agassiz  in  honor  of  the  great  scientist  who  did  so 
much  toward  the  explanation  of  glacial  phenomena.  Gla- 
cial lake  plains  of  this  kind  are  found  hot  infrequently. 
They  now  form  fertile  areas  of  great  agricultural  value. 

172.  Waterfalls  Due  to  Glaciation.  —  As  the  ice  spread 
over  the  country  it  filled  the  river  valleys  in  many  places 
with  debris.  When  the  ice  melted  away,  some  rivers 
could  no  longer  find  their  old  courses  and  were  forced  to 
seek  new  ones.  It  frequently  happened  that  in  deepen- 
ing these  new  channels  the  river  came  upon  buried  ledges, 
and  in  wearing  these  down,  rapids  and  falls  were  devel- 
oped. In  this  way  many 
of  the  water  powers  of 
New  England  and  the 
northern  states  were 
produced. 

The  Merrimac  fur- 
nishes a  fine  example  of 
water  power  due  to 
glaciation.  The  great 
manufacturing  cities  of 


NIAGARA  FALLS. 

Due  to  rearrangement  of  the  drainage 
by  the  ice  of  the  Glacial  Period. 


Lowell,  Lawrence  and 
Haver  hill  would  not  exist  had  not  the  river  been  displaced 
from  its  previous  channel  by  the  glacial  ice,  and  in  devel- 
oping its  new  valley  come  upon  ledges  which  it  is  now 
trying  to  reduce  to  grade.  The  Niagara  is  another  notable 
example  of  vast  water  power  due  to  the  displacement  of 
drainage  by  the  ice.  It  is  probable  that  in  pre-glacial  time 
there  was  a  river  which  carried  off  the  drainage  of  the  area 
now  drained  by  the  Niagara,  but  it  did  not  flow  where  the 
Niagara  now  flows. 

173.  Glacial  Period.  —  Evidences  of  an  ancient  ice  cov- 
ering are  seen  in  North  America,  even  as  far  south  as  the 
Ohio  River  and  extending  over  a  vast  region  which  now 


GLACIAL  PERIOD 


383 


enjoys  a  temperate  climate.  The  greatest  ice  invasion 
during  this  period  extended  from  northern  Canada  across 
New  England  into  the  sea,  across  the  basins  of  the  Great 


AREA  COVERED  BY  THE  ICE  OF  THE  GLACIAL  PERIOD. 

Lakes  and  the  upper  Mississippi  valley  and  across  a  part 
of  the  Missouri  valley.  It  wrapped  in  its  icy  mantle  al- 
most the  entire  region  between  the  Ohio  and  Missouri 
rivers  and  the  Atlantic  Ocean. 

Another  great  ice  invasion  spread  out  from  the  high- 
lands of  Scandinavia.     As  in  later  days  the  Norsemen,  so 


384  FIRST   YEAR   SCIENCE 

at  that  time  the  glacial  ice  overspread  northern  Europe, 
carrying  Scandinavian  bowlders  across  the  Baltic  and  what 
is  now  the  basin  of  the  North  Sea,  fdrerurmers  of  the 
Scandinavian  sword  which  in  later  ages  carried  devasta- 
tion to  these  regions. 

The  thickness  of  the  ice  over  these  central  areas  was  very 
great,  probably  approaching  a  mile.  The  pressure  on  the 
ground  below  must  have  been  tremendous  and  the  scouring 
and  erosive  effect  vast  indeed.  The  soil  which  previously 
covered  the  surface  was  swept  away  and  borne  toward  the 
ice  margin,  leaving  the  rocks  smoothed  and  bare. 

Prehistoric  man  probably  saw  the  great  ice  mantle ;  he 
may  even  have  been  driven  from  his  hunting  grounds  by 
its  slow  encroachment.  His  rude  stone  implements  are 
found  mingled  with  the  glacial  gravels.  But  like  the 
spreading  ice  he  has  left  no  record  from  which  the  time 
or  cause  of  the  Crlacial  Period  can  be  determined. 

174.  Effect  of  the  Glacial  Period  upon  Plants  and  Animals.  — 
All  plants  and  animals  were  forced  either  to  migrate  be- 
fore the  slowly  advancing  ice  or  to  suffer  extermination. 
Individual  plants,  of  course,  could  not  move,  but  as  the  ice 
spread  toward  the  south  with  extreme  slowness  and  with 
many  halts,  the  plants  of  colder  latitudes  found  conditions 
suitable  for  their  growth  ever  opening  toward  the  south. 
They  were  thus  induced  to  spread  in  that  direction,  so 
that  at  the  time  of  the  greatest  extension  of  the  ice  the 
plants  suitable  to  a  cold  climate  had  penetrated  far  to  the 
south  of  their  former  habitat. 

As  the  ice  receded,  these  cold-loving  plants  were  forced 
to  follow  its  retreat  or  to  climb  the  mountains  in  order  to 
obtain  the  climate  they  needed.  They  did  both,  so  that 
in  areas  covered  by  the  ice,  plants  similar  to  those  of  far 
northern  regions  are  found  on  the  tops  of  the  mountains 
in  middle  latitudes.  What  was  true  of  the  plants  was 


MAN  AND   THE  GLACIAL   PERIOD 


385 


true  also  of  the  animals.  Thus  the  conditions  at  the 
time  of  the  Glacial  Period  explain  some  of  the  most  diffi- 
cult problems  in  Botany  and  Zoology. 

175.  Man  and  the  Glacial  Period.  —  Although  the  Glacial 
Period  occurred  thousands  of  years  ago,  probably  before 
man  was  widely  spread 
over  the  earth's  surface, 
yet  its  influence  upon 
him  has  been  most 
marked.  His  manufac- 
turing .depends  largely 
for  its  power  upon  the 
falls  and  rapids  due 
to  the  rearrangement 
which  the  glaciers  made 


in  the  drainage.      Some  ELECTRIC  PLANT  AT  NIAGARA. 

of  the    most   fertile   soil  Man's  use  of  the  power  which  the 

Of    middle    latitudes    is  .         Skiers  arranged  for  him. 

due  to  the  pulverized  rock  left  unexhausted  by  plant  life  as 
the  glacier  retreated.  Since  the  soil  was  largely  brought 
from  the  inhospitable  northern  regions  where  man  cannot 
easily  exist,  it  has  increased  the  extent  of  arable  land 
suitable  for  his  cultivation. 

By  the  mingling  of  unweathered  yet  valuable  soil-pro- 
ducing rocks  over  the  surface,  the  permanence  of  the 
soil's  fertility  has 'been  increased,  although  the  difficulty 
of  tillage  is  greater.  The  surface  has  been  beautified  by 
innumerable  lakes  which  furnish  man  excellent  water  sup- 
plies and  restrain  the  rivers  from  excessive  floods.  Glacial 
lake  beds  of  great  productiveness  have  been  formed  for 
his  cultivation.  Hardy  plants  from  the  north  have  been 
brought  to  cover  the  mountain  sides  in  middle  latitudes. 
In  fact,  man's  whole  condition  in  these  latitudes  has  been 
modified  by  the  ancient  ice  invasion. 


386  FIRST   YEAR   SCIENCE 

176.  Wind  Work.  —  The  wind  must  be  considered  among 
the  forces  affecting   the    earth   in   its   relation    to   man. 
Whenever  the  wind  blows  over  dry  land;-  particles  of  dust 
and  sand  are  blown  away  and  deposited  elsewhere.     The  in- 
teriors of  our  houses  often  become  covered  with  dust  blown 
from  the  dry  streets.     Even  on  ships  at  sea,  thousands  of 
miles  from  land,  dust  has  been  collected. 

In  volcanic  eruptions  great  quantities  of  dust  are  thrown 
into  the  air  and  spread  broadcast  over  the  earth.  On  the 
highest  and  most  remote  snow  fields  particles  of  this  dust 
have  been  found.  In  the  great  eruption  of  Krakatoa,  dust 
particles  made  the  complete  circuit  of  the  earth,  remaining 
in  the  air  and  causing  a  continuance  of  red  sunsets  for 
months. 

Sand  is  not  carried  as  far  as  dust,  but  at  times  of  strong 
wind  it  is  often  borne  for  long  distances.  Even  houses, 
trees  and  stones  of  considerable  size  may  be  lifted  and 
moved  by  a  fierce  wind  storm.  The  wind-swept  detritus 
has  been  known  even  to  obstruct  and  modify  the  course  of 
streams.  Where  the  wind  blows  dust  constantly  in  one 
direction,  deposits  of  great  thickness  are  sometimes  made. 

In  Kansas  and  Nebraska  there  are  beds  of  volcanic  dust, 
reaching  in  some  places  to  a  thickness  of  more  than  a 
score  of  feet  and  yet  there  are  no  known  volcanoes  either 
past  or  present  within  hundreds  of  miles.  In  China  there 
is  a  deposit  of  fine  dustlike  material,  in  some  places  a 
thousand  feet  thick,  which  is  thought  by  some  to  be  wind 
blown.  This  forms  a  very  fertile  and  fine-textured  soil 
and  supports  a  great  population.  Many  of  the  inhabitants 
of  the  region  live  in  caves  dug  in  the  steep  banks  of  the 
streams,  so  firm  and  fine  textured  is  the  material.  Wind 
deposits  of  this  kind  are  called  loess  beds. 

177.  Wind  Erosion.  —  Not  only  does  the  wind  take  up 
particles  of  dust  and  sand  and  carry  them  from  one  place 


SAND  DUNES 


387 


to  another,  but  it  uses  these  particles  to  cut  and  erode  ob- 
stacles in  its  path.  The  artificial  sand  blast  is  in  common 
use.  In  it  a  stream  of  sand  is  driven  with  great  velocity 
upon  an  object  which  it 
is  desired  to  etch.  In 
nature  the  same  kind  of 
etching  is  done  by  the 
wind-blown  sand. 

The  glasses  in  the 
windows  of  lighthouses 
along  sandy  coasts  are 
sometimes  so  etched  as 
to  lose  their  transpar- 
ency. Rocks  exposed  to 
the  winds  are  carved 
and  polished;  the  softer 


BEma  DUQ  vf  By  THE 


parts    are    worn    away 

more  rapidly  than  the  harder  parts,  just  as  in  all  other 
forms  of  erosion.  In  certain  regions  where  the  prevailing 
winds  are  in  one  direction,  one  side  of  exposed  rocks  is 
found  to  be  polished,  while  the  other  sides  remain  rough. 

178.  Wind  Burying  and  Exhuming.  —  In  exposed  sandy 
regions  where  there  are  strong  winds,  objects  which  ob- 
struct the  movement  of  the  air  cause  deposition  of  the 
transported  sand   just  as  obstructions  in  flowing  water 
cause  sediment  to  be  deposited.     And  just  as  sand  bars 
may  be  deposited  by  a  river  and  then  carried  away  again, 
owing  to  a  change  in  the  condition  of  the  river's  load,  so 
forests  and  houses  in  sandy  regions  are  sometimes  buried, 
to  be  uncovered  again  perhaps  by  a  change  in  the  load 
carried  by  the  wind.   ' 

179.  Sand  Dunes.  —  Sand-laden  wind  generally  deposits 
its  burden  in  mounds  and  ridges  called  sand  dunes  (page 
302).     When  once  a  deposition  pile  begins,  it  acts  as  a 


388  FIRST   YEAR   SCIENCE 

*  .  ** 

barrier  to  the  wind  and  thus  causes  its  own  further  growth. 
In  great  deserts  where  the  wind  is  generally  from  one 
direction  these  sand  dunes  sometimes  grow  to  a  height  of 
several  hundred  feet,  but  usually  they  are  not  more  than 
20  or  30  feet  high. 

They  generally  have  a  gentle  slope  on  the  windward 
side  and  a  steep  slope  on  the  leeward  side.     The  sand  is 


A  FOREST  ON  CAPE  COD. 
The  trees  are  being  engulfed  in  wind-blown  sand. 

continually  being  swept  up  the  windward  side  over  the 
crest,  thus  causing  the  dune  to.  move  forward  in  the  direc- 
tion in  which  the  prevailing  wind  blows.  (Fig.  117.) 

Dunes  make  travel  difficult,  as  both  in  climbing  and 
descending  the  traveler  sinks  into  the  yielding  sand.  Al- 
most no  plant  life  can  find  lodgment  in  these  shifting 
sand  piles,  so  the"'  wind  continually  finds  loose  sand  on 
which  to  act,  and  a  dune  country  is  always  a  region  of 
shifting  sands.  As  the  dunes  move  in  the  direction  of 
the  prevailing  wind  they  sometimes  invade  a  fertile  coun- 


SUMMARY 


389 


try,  so  that  it  becomes  necessary  if  possible  to  find  a  way 
to  check  their  movement.  This  has  been  done  in  some 
places  by  planting  certain  kinds  of  grasses  capable  of 
growing  in  the  sand  and 
thus  protecting  the  sand 
particles  from  the  action 
of  the  wind.  "*"' 


Sand  dunes  are  found 


Fig.   117. 


along  almost  all  low  sandy  coasts,  and  they  render  difficult 

the  building  and  maintenance  of  roads  and  railroads  to 

many  beach  towns. 

Summary.  —  Besides  the  sculpturing  of  waves  and  rivers, 

two  other  agents  of  erosion  are  glaciers  and  winds.     Alpine 

glaciers  are  formed  by 
huge  masses  of  ice  and 
snow  crowding  into 
mountain  valleys  where 
the  snow  never  melts 
entirely.  Glaciers  are 
intersected  by  great 
cracks  called  crevasses 
and  they  carry  accumu- 
lations of  debris  called 


QUARRYING  A  SAND  DUNE  TO  MAKE 
BRICK. 


moraines.  Icebergs  are 
the  ends  of  glaciers 
which  have  broken  off. 

The  northern  part  of  America  was  once  covered  by  a  huge 
glacier  at  a  time  which  we  call  the  G-lacial  Period.  This 
glaciation  has  had  a  great  effect  upon  the  region  covered. 
Glaciers  smooth  out  irregularities  in  the  surface,  grind 
rocks,  transport  soil  and  bowlders,  dam  lakes,  force  rivers 
to  seek  new  channels  and  on  account  of  this  create  water- 
falls. Thus  the  glaciers  of  the  Glacial  Period  have  had  a 
great  influence  upon  the  conditions  of  life. 


390  FIRST   YEAR   SCIENCE 

The  winds  not  only  blow  the  clouds  about  over  the 
land,  but  they  bear  dust  and  sand  with  which  they 
sculpture  and  erode  rocks  and  cliffs.  +They  also  build  up 
sand  dunes  and  by  moving  them  over  the  surface  of  the 
land  sometimes  destroy  forests  and  fields. 

QUESTIONS 

How  are  glaciers  formed?  Where  are  they  found?  What  do 
they  do  ? 

How  large  and  how  thick  is  the  Greenland  icefield  ? 

How  are  icebergs  formed'?     Why  are  they  dangerous  V 

Describe  the  different  kinds  of  deposits  and  formations  due  to 
glaciers. 

How  are  glacial  lakes  such  as  Lake  Agassiz  formed?  Why  are 
they  fertile  when  drained  ? 

Some  waterfalls  are  due  to  glaciation.     Why? 

What  was  the  extent  of  the  North  American  ice  sheet  during  the 
Glacial  Period? 

What  has  been  the  effect  of  the  glacial  period  upon  plants,  animals 
and  man  ? 

In  what  ways  has  the  wind  modified  the  surface  of  the  earth  ? 

How  are  sand  dunes  formed  ?  WThy  are  they  destructive  to  plant 
life? 


CHAPTER   XII 

LOW  AKEAS  OF  THE  EAKTH 

180.  Level  Areas.  —  At  different  places  on  the  earth's 
surface  there  are  broad  extents  of  nearly  level  land.  Here 
the  drainage  is  often  poorly  developed,  and  there  are  slight 
depressions  often  of  considerable  area.  After  a  rainfall  the 


A  LEVEL,  POORLY  DRAINED  AREA. 
Such  an  area  is  called  young. 

shallow  water  stands  in  these  depressions  until  it  evapo- 
rates or  sinks  into  the  ground.  In  the  parts  where  the 
drainage  has  been  developed,  the  streams  flow  with  slow 
currents  in  channels  of  little  depth. 

When  excavations  are  made,  the  rock  beneath  the  soil  is 
often  found  in  horizontal  or  almost  horizontal  layers. 
Where  the  elevation  of  these  areas  is  considerable,  the 
streams  may  have  deep  gorges  and  the  surface  may  be  well 
dissected.  Where  these  level  areas  are  low,  they  are  called 

391 


392  .-FIRST   YEAR   SCIENCE 

•  >  j* 

plains,  and  where  high,  especially  if  surrounded  by  steeply 
descending  sides,  they  are  called  plateaus.  A  good  ex- 
ample of  the  low,  level  area  is  the  plain  bf  northern  Russia 
and  of  the  high  area,  the  Arizona  Plateau  through  which 
flows  the  famous  Colorado  River. 

181.  Coastal  Plains.  —  Experiment  130.  — Fill  a  tall  glass  jar 
nearly  full  of  water.  Pour  into  this  very  slowly  a  mixture  of  sand 
and  finely  pulverized  clay.  Note  the  effect  upon  the  color  of  the 
water.  Allow  the  water  to  stand  for  several  days  and  then  examine 
the  deposition  on  the  bottom  of  the  jar.  Are  the  sand  and  clay  now 
mixed  as  they  were  when  poured  into  the  jar?  What  effect  has  the 
water  had  upon  the  mixture  ? 

We  have  already  seen  that  the  surface  of  the  earth  is 
not  stable,  but  is  subject  to  movements.  If  the  land  bor- 
dering a  coast  rises  or  the  bottom  of  the  ocean  is  depressed, 
it  causes  the  water  to  withdraw  from  the  land,  and  a 
strip  of  what  was  formerly  sea  bottom  is  changed  into  dry 
land. 

This  new  area  is  composed  of  clays,  sands  and  gravels, 
often  containing  shells  similar  to  those  found  on  the 
neighboring  shores.  The  surface  is  comparatively  flat, 
but  slightly  irregular,  and  the  drainage  lines  have  not  as 
yet  been  established.  The  water  that  falls  here  which 
neither  evaporates  nor  sinks  into,  the  soil  runs  into  the 
slight  depressions  and  makes  shallow  lakes.  When  these 
become  full,  the  water  finds  an  outlet  into  a  lower  region 
until  at  last  it  works  its  way  to  the  sea. 

These  outlet  streams  gradually  establish  themselves 
and  form  a  continuous  line  of  streams  and  pools  reaching 
to  the  sea,  with  broad,  poorly  drained  areas  lying  between. 
The  streams  at  once  begin  to  cut  down  their  beds  and  the 
pools  to  fill  up  with  the  silt  washed  into  them,  until  at 
last  all  the  pools  are  drained  and  a  network  of  streams 
carries  the  run-off  into  the  sea. 


COASTAL  PLAINS  393 

Usually  the  dry  land  of  the  coastal  plain  has  appeared 
very  gradually,  with  long  periods  when  there  was  no  gain 
in  its  extent.  Sometimes  the  waste  brought  to  the  ocean 
was  of  a  different  kind  from  what  it  was  at  other 
times.  Thus  the  character  and  condition  of  the  material 
composing  the  plain  .vary  considerably,  but  all  the  strata 
are  usually  inclined  slightly  toward  the  sea.  The  bounda- 
ries of  the  different  kinds  of  hard  and  soft  material  com- 
posing the  plain  are  approximately  parallel  to  the  old 
shore  line.  The  plain  will  thus  become  a  belted  plain. 

As  streams  wear  back  faster  in  the  soft  than  in  the  hard 
material,  the  side  streams  become  longer  in  the  soft  layers 
than  in  the  hard,  and  in  time  streams  of  considerable 
length  are  found  running  in  a  direction  nearly  parallel  to 
the  old  coast.  These  have  their  outlets  through  streams 
which  run  down  from  the  old  land  across  the  plain,  so 
that  the  general  appearance  of  the  drainage  is  something 
like  a  lengthwise  cross  section  through  the  trunk  and 
limbs  of  an  oak. 

When  mixtures  of  different  materials  are  deposited  in 
water,  the  coarsest  sinks  first  and  the  finest  last  (Exp.  130). 
We  should  thus  expect  that  of  the  material  brought  down 
by  the  river  the  coarser  layers  would  lie  back  from  the 
coast.  This  is  often  true,  although  there  is  frequently 
uncovered  near  the  border  of  the  old  land  back  from  the 
coast  a  belt  of  easily  eroded  material,  and  a  lowland  of 
erosion  is  formed  in  this  by  the  streams.  The  Delaware 
River  from  Trenton  to  Wilmington  and  the  Alabama  River 
between  Montgomery  and  Selma  flow  through  such  low- 
lands. These  regions  are  called  inner  lowlands  and  possess 
a  fertile,  fine-textured  soil,  generally  the  best  to  be  found 
in  the  coastal  plain  area. 

This  inner  lowland  is  bordered  on  the  landward  side  by 
the  old  land,  usually  composed  of  firmly  compacted  rocks 


394 


•..  FIEST   YEAR   SCIENCE 


which  often  contain  valuable  minerals  and  building  stones. 
On  the  seaward  side  it  is  bordered  by  the  rather  abruptly 
ascending  edge  of  the  coarse  material  bf  the  plain  which 
has  not  yet  been  removed.  From  the  top  of  this  ridge  there 
is  a  gradual  slope  toward  the  sea.  As  the  region  back  to- 
ward the  old  land  is  higher,  and  has  been  above  the  sea 


FE  SAVING  STA. 


Ft  SAVING  STA.          »5^ 


I  SAVING  STA. 
JABSECON  LIGHT      ^ 


THE  COAST  NEAR  ATLANTIC  CITY. 
Showing  marshes,  lagoons  and  sand  reefs. 

and  exposed  to  erosion  longer,  it  is  much  more  dissected 
than  the  surface  nearer  the  sea  and  is  much  more  irregular 
and  hilly. 

A  coastal  plain  is  a  gradually  emerged  sea  bottom,  and 
so  has  shallow  water  extending  out  for  a  considerable  dis- 
tance from  its  edge.  Along  the  shore  are  marshes  and 


COASTAL  PLAINS 


395 


lagoons  bordered  on  their  seaward  side  by  sand  reefs, 
where  the  winds  have  piled  up  the  sand  brought  in  by 
waves.  In  some  places  these  sand  reefs  are  so  situated 
that  they  are  valuable  for  habitation,  as  at  Atlantic  City, 


RICE  SWAMP  AT  THE  BORDER  OF  A  NARROW  COASTAL  PLAIN. 

New  Jersey,  where  a  large  summer  resort  has  grown  up, 
or  along  the  coast  farther  south,  where  a  sparse  popula- 
tion finds  its  home  on  the  broader  reef. 

A  coastal  plain  increasing  in  width  toward  the  south 
extends  from  New  York  to  the  Gulf.     The  western  coast 


396 


.-  FIRST   Y.EAE   SCIENCE 


of  Europe  has  a  considerable  plain  of  this  kind.  The 
Netherlands  are  situated  on  land  which  has  been  either 
reclaimed  from  the  sea  naturally  in  recent  geological  time 
or  artificially  by  man  in  recent  historical  time.  In  the 
southern  part  this  reclamation  is  largely  due  to  the  sedi- 
ment brought  down  by  the  Rhine. 

Sometimes  the  materials  of  a  coastal  plain  are  found 
far  inland  in  places  which  are  now  separated  from  the  sea 
by  mountain  ranges,  as  near  Lake  Ontario.  But  the 
method  of  formation  was  the  same,  only  thousands  upon 
thousands  of  years  have  passed  since  these  rocks  were  ex- 
posed, and  vast  geological  changes  have  taken  place  in  that 
time.  Such  areas  as  these  are  sometimes  called  ancient 
coastal  plains. 

In  the  western  part  of  the  United  States  the  coastal 
plain  is  not  as  well  developed  as  on  the  Atlantic  border. 
But  the  region  about  Los  Angeles  is  a  coastal  plain,  and 

almost  all  the  charac- 
teristics of  the  broad 
eastern  plain  can  be 
seen  in  traveling  from 
the  ocean  to  the  coast 
mountains. 

182.  Industries  on 
Coastal  Plains.  —  The  val- 
uable minerals  of  the 
earth  are  usually  found 
in  the  older  rocks,  so 
there  is  no  mining  on  a 
coastal  plain,  and  be- 


CRUDB  TURPENTINE  STILL. 

In  the  pine  belt  of  the  North  Carolina 

coastal  plain. 


cause  the  rivers  are  shallow  and  fall  over  no  ledges  as 
they  flow  across  these  plains,  no  great  water  power  for 
manufacturing  can  be  developed.  The  sluggish  streams 
are  often  dammed  and  small  water  powers  developed,  but 


COASTAL   PLAIN  INDUSTRIES 


397 


there  is  not  the  fall  necessary  for  large  factories,  except 
sometimes  in  the  hilly  region  back  near  the  old  land  where 
the  rivers  have  developed  rather  deep  and  narrow  valleys, 
and  mill  ponds  of  considerable  size  may  be  made. 

As  the  different  kinds  of  soil  lie  in  belts,  agriculture 
will  vary  with  the  belts.  In  warm  climates  rice  can  be 
raised  along  the  shore 
where  the  land  is 
marshy.  On  the  sandy 
land  most  profitable 
truck  farming  is  possi- 
ble if  the  transportation 
facilities  are  good.  In 
many  places  in  the 
southern  states  these 
sandy  areas  support  fine 
forests  of  pine  (page 
198)  which  are  most  val- 
uable for  the  production 
of  turpentine,  tar  and 
lumber.  Where  the  soil 
is  not  too  sandy,  cotton 
is  raised  in  abundance. 
The  materials  for  mak- 


COTTON. 


A  most  valuable  product  of  the  southern 
coastal  plain. 


ing  glass,  pottery  and 
brick  are  widespread 
over  coastal  plains. 

The  cities  on  coastal  plains  are  usually  found  either 
(1)  near  the  coast,  where  the  rivers  have  formed  harbors 
and  -so  have  made  ocean  commerce  possible,  or  (2)  at 
the  head  of  navigation  in  the  rivers  where  water  transporta- 
tion begins,  or  (3)  still  farther  up  the  river  at  the  fall  line, 
where  manufacturing  on  a  large  scale  is  possible. 

Tlnefall  line  is  the  point  on  a  river  where  its  bed  passes 


398 


FIRST   TEAR   SCIENCE 


from  the  harder  rock  of  the  old  land  to  the  softer  material 
of  the  coastal  plain.  The  softer  material  is  worn'away  more 
easily  than  the  hard  material,  and  falls  or  rapids  are  pro- 
duced suitable  for  water  power.  A  glance  at  a  map  of 
the  southeastern  United  States  will  show  that  the  princi- 


PlNEAPPLES. 

A  valuable  crop  of  the  southern  coastal  plain. 

pal  cities  lie  in  lines  nearly  parallel  to  the  coast.  Of  those 
near  the  coast  are  Norfolk,  Wilmington,  Charleston, 
Savannah,  Jacksonville ;  at  the  fall  line,  Trenton,  Phila- 
delphia, Richmond,  Columbia  and  Augusta. 

Coastal  plains  furnish  a  most  suitable  place  for  the 
boring  of  artesian  wells.  As  the  strata  are  diversified  in 
structure  and  all  dip  gently  toward  the  sea,  porous  strata 
inclosed  above  and  below  by  impervious  strata  are  readily 
found.  When  the  upper  of  these  are  tapped,  water  is  forced 
by  hydraulic  pressure  to  a  height  nearly  equal  to  the 


EMBAYED  PLAINS 


399 


highest  point  reached  by  the  upper  stratum.     Much  of  the 
drinking  water  on  coastal  plains  is  obtained  in  this  way. 

183.  Embayed  Plains.  —  If  a  coastal  plain  is  submerged 
after  it  has  been  somewhat  eroded,  the  water  backs  up 
into  the  stream  valleys  and  forms  reentrant  bays.  The 
little  side  streams  which  enter  into  the  main  streams  near 


m 


A  SUBMERGED  COASTAL  PLAIN. 

the  coast  no  longer  flow  into  these  streams  but  into  the 
bays.  If  the  country  is  somewhat  thoroughly  dissected 
near  the  coast,  there  will  be  many  small  bays.  The  inter- 
stream  areas  will  project  out  like  long  fingers  with  water 
between  them. 


400  .FIRST   YEAR   SCIENCE 

The  effect  of  a  submerged  and  eroded  coastal  plain  is 
seen  in  the  Delaware  and  Chesapeake  bay  region.  Here 
the  old  river  courses  have  been  submerged,  and  the  land  be- 
tween the  rivers  extends  into  the  ocean  in  narrow,  rather 
flat  strips  with  many  little  inlets  along  the  sides.  Easy 
water  communication  is  here  possible  to  a  considerable 
distance  inland  and  to  almost  every  part  of  the  land  sur- 
face near  the  coast. 

When  the  country  was  first  settled,  these  water  courses 
were  most  advantageous  to  the  settlers,  as  the  produce  of 
the  farms  could  be  transported  to  sea-going  ships  with 
comparatively  little  difficulty,  much  more  easily  than  would 
have  been  the  case  if  it  had  been  necessary  to  carry  it  by 
land.  There  was  little  need  of  building  roads,  as  each 
farmer  had  a  protected  water  highway  to  his  door.  Thus 
a  part  of  this  region  was  known  as  "  Tide-water  Virginia." 

184.  Lake  Plains.  —  Lakes  which  receive  the  drainage 
from  the  land  gradually  have  their  floors  smoothed  over  by 
the  sediment  which  the  streams  bring  to  them  and  the 
waves  and  currents  spread  out.  The  lake  itself  is  thus 
filled,  or  in  time  the  outlet  wears  back  so  as  to  drain 
the  lake.  Thus  a  plain  is  left,  the  elevation  of  which  is 
determined  by  the  elevation  of  the  old  lake  bed. 

During  the  Glacial  Period  lakes  were  held  in  at  some 
places  by  huge  dams  of  ice  and  at  other  places  by  accumu- 
lations of  sand  or  gravel  brought  down  by  the  glaciers  and 
deposited  so  as  to  obstruct  the  valleys.  The  ice  has  now 
disappeared  and  the  gravelly  material  has  often  been  easily 
eroded,  so  that  lake  plains  are  not  uncommon  in  the  north- 
ern United  States.  As  the  soil  of  these  plains  is  fine  and 
easily  cultivated,  they  furnish  excellent  farm  lands. 

As  already  stated,  a  plain  of  this  kind,  remarkable  for  its 
fertility  and  extent,  is  drained  by  the  Red  River  of  the 
North  and  comprises  the  eastern  part  of  North  Dakota  and 


RIVER  PLAINS 


401 


about  half  of  the  Province  of  Manitoba.  A  somewhat 
similar  plain  is  found  in  northern  New  York,  bordering 
Lake  Ontario.  This  was  formed  at  the  time  when  the  out« 
let  of  the  lake  was  the  Mohawk  River,  the  present  outlet 
then  being  obstructed  by  ice.  The  ice  dam  has  since 


.      •'...,.'  riwfe 


LAKE  PLAIN. 
The  ice  dam  in  this  lake  has  recently  receded. 

melted,  the  lake  has  been  lowered,  and  a  part  of  its  old  bed 
has  been  exposed. 

A  change  in  the  amount  of  rainfall  may  cause  the  for- 
mation of  a  lake  plain.  If  not  as  much  water  is  furnished 
to  the  lake  as  evaporates,  the  lake  dries  up  and  exposes 
its  bed  as  a  flat  plain  with  perhaps  a  small  remnant  of  the 
former  lake  still  existing  at  the  lowest  part.  Such  is  the 
region  around  Great  Salt  Lake,  Utah. 

185.  River  Plains.  —  Sometimes  a  river  widens  its  valley 
enough  so  that  it  swings  slowly  from  one  side  to  the  other, 
and,  at  high  water,  floods  the  valley  for  a  considerable 
distance  on  either  side  of  its  course.  A  low,  flat  plain  is 
thus  developed,  sometimes  terminating  near  the  mouth  of 
the  river  in  a  delta. 


402  .FIRST   YEAR   SCIENCE 

These  plains  are  very  fertile  and  are  usually  called 
"  bottom  lands  "  by  the  farmers.  They  are  often  unhealthy 
because  of  floods  and  poor  drainage.  Where  the  water  in 
the  river  rises  rapidly  and  to  a  considerable  height,  it  is 
dangerous  to  inhabit  these  plains.  Thus  it  is  necessary 
to  build  strong  levees  along  the  river  bank,  as  in  the  case 
of  the  lower  Mississippi  and  some  of  its  tributaries.  But 


"  BOTTOM  LANDS." 

sometimes  these  plains  are  so  fertile  that  they  are  densely 
populated,  as  the  plain  of  the  Ganges. 

186.  Prairies  of  the  United  States.  — North  of  the  Ohio 
River  and  extending  westward  beyond  the  Mississippi  is  a 
region  of  rolling  land  with  a  deep,  rich  soil.  Early  in  the 
last  century  it  began  to  be  rapidly  populated  on  account 
of  its  great  agricultural  advantages.  Owing  partly  to  the 
fineness  of  the  soil,  but  mostly  to  the  frequent  burning  over 
of  the  region  by  the  Indians,  the  area  was  destitute  of  trees 
except  in  some  places  along  the  river  courses. 

Thus  the  emigrant  did  not  need  to  go  to  the  trouble  and 
delay  of  clearing  the  forests  before  beginning  to  farm. 
Cultivation  could  begin  in  earnest  with  the  first  spring, 


THE  GEE  AT  PLAINS  403 

and,  as  a  rule,  rich  harvests  could  be  obtained.  The  soil 
here  is  transported  soil ;  it  is  deep  and  unlike  that  of  the 
underlying  rock.  In  some  places  it  is  rather  stony  and  in 
others  very  fine  and  without  stones.  It  is  so  deep  that  the 
underlying  rock  is  only  seen  in  deep  cuts. 

This  soil  was  probably  deposited  by  the  great  conti- 
nental  glaciers  which  once  covered  the  region  and  was 


ALFALFA  CUTTING  ON  THE  FERTILE  PRAIRIES. 

spread  out  either  by  the  action  of  the  slowly  moving  ice 
or  by  the  water  from  the  melting  ice.  This  water  flowed 
over  the  surface  in  shallow  debris-laden  streams,  bearing 
their  silt  into  the  still  waters  of  transient  ice-dammed 
lakes.  Whatever  the  original  surface  of  the  region,  at 
present  it  is  an  irregularly  filled  plain  due  to  the  ancient 
ice  sheet.  As  the  soil  is  composed  of  pulverized  rock  not 
previously  exhausted  by  vegetable  growth  it  is  strong  and 
enduring,  so  that  this  country  has,  since  its  settlement, 
been  noted  for  its  productivity. 

187.  The  Great  Plains  of  the  United  States.  —  West  of  the 
Mississippi  River,  and  merging  almost  imperceptibly  into 
the  prairie  region  on  the  north  and  the  coastal  plain  region 
on  the  south,  there  is  a  broad  extent  of  territory  usually 


404 


FIRST   TEAR   SCIENCE 


called  the  Great  Plains.  This  region  consists  of  irregular 
intrenched  valleys  50  to  100  feet  deep.  Sometimes  there 
are  hills  and  mountains,  but  viewed  from  an  eminence  the 
country  appears  flat. 

The  elevations,  are  either  flat  topped  hills,  the  strata  of 
which  are  slightly  inclined  and  correspond  in  position  to 
those  found  in  the  plain  beneath,  or  they  are  masses  of  ig- 


A  HIGH,  DRY  PLAIN. 

neous  material  which  appear  to  have  been  thrust  up  through 
the  rock  surrounding  them.  In  the  former  case  the  ele- 
vations are  simply  remnants  of  the  layers  of  rocks  which 
once  extended  over  the  country,  but  which  have  now  been 
eroded  away  over  the  larger  part  of  it ;  in  the  latter  case 
they  are  the  igneous  masses  which  have  withstood  erosion. 
The  Great  Plains  may  thus  be  considered  as  an  example 
of  a  plain  of  erosion. 

Here,  as  in  the  prairie  region,  trees  are  wanting,  but 
their  absence  is  due  rather  to  the  lack  of  the  necessary 
rainfall  than  to  the  reasons  assigned  for  the  former  region. 
Although  formerly  considered  almost  a  desert  on  account 
of  its  small  rainfall,  this  region  now  supports  vast  herds 


LIFE  ON  PLAINS 


405 


of  cattle,  and  by  the  aid  of  irrigation  will  soon  possess 
great  agricultural  wealth. 

188.  Life  on  Plains.  —  The  life  conditions  on  plains  are 
very  different  from  those  in  places  where  the  irregularities 
of  the  surface  are  great.  The  climate  of  plains  is  quite 
uniform  and  depends  to  a  large  extent  upon  their  position 
on  the  earth's  surface.  Movement  is  as  easy  in  one  direc- 
tion as  in  another,  and  the  lines  of  travel  tend  to  be 


A  HERD  OF  CATTLE  ON  THE  GREAT  PLAINS. 

straight.  There  is  usually  no  reason  for  an  accumulation 
of  population  in  any  one  place,  so  the  population  tends  to 
be  uniformly  distributed. 

As  movement  from  place  to  place  is  easy,  it  is  not  dif- 
ficult for  the  inhabitants  of  a  plain  to  mass  themselves 
together  at  one  point.  In  case  of  invasion  by  a  superior 
enemy  there  is  no  place  for  hiding  or  safe  retreat,  and  sub- 
jection or  extermination  are  the  alternatives,  unless  the 
plain  is  so  large  that  the  enemy  is  unable  to  spread  over 
it.  In  the  case  of  animals  this  has  been  shown  in  the 
practical  extermination  of  the  American  bison  and  ante- 
lope. In  the  case  of  men  it  was  shown  on  the  plains  of 
Russia  in  the  thirteenth  century  when  the  Tartars  con- 
quered the  region  and  threatened  to  overrun  Europe. 


406  FIRST   YEAR   SCIENCE 

1  .  ^* 

Another  instance  was  that  of  the  fatal  invasion  of 
Russia  by  Napoleon.  The  Russians,  unable  to  find  a 
strategic  place  to  make  a  stand,  retreated  farther  and 
farther  into  the  plain.  The  depletion  of  Napoleon's  army, 
due  to  the  extent  of  territory  which  must  be  held  in  his 
rear,  the  distance  from  his  base  of  supplies  and  the  rigor 
of  the  Russian  winter,  forced  him  to  begin  that  disastrous 


HERD  OF  BISON. 

retreat,  the  fatal  results  of  which  probably  led  to  his  final 
overthrow. 

The  effect  of  plains  on  the  distribution  of  population  is 
shown  in  the  early  settlements  on  the  coastal  plain  terri- 
tory south  of  Philadelphia.  Here  there  were  almost  no 
towns  containing  as  many  as  twenty  houses  until  the 
colonies  had  been  settled  for  nearly  two  hundred  years, 
and  even  now  cities  of  considerable  size  are  rare,  but  on 
the  more  rugged  lands  of  the  north  the  tendency  to  build 
towns  began  at  the  beginning  of  settlement. 

189.  Plains  in  History.  —  Plains  have  always  played  an 
important  part  in  history.  Here  armies  can  march  and 
countermarch  with  comparative  ease.  Large  bodies  of 


SUMMARY 


407 


PART  OF  THE  PLAIN  OF  WATERLOO, 
BELGIUM. 


men  can  easily  be  assembled.  Military  stores  can  be 
readily  collected  and  all  the  operations  of  war  carried  on 
without  natural  obstructions.  Thus  it  happens  that  cer- 
tain plains  have  been  the 
seats  of  almost  innumer- 
able wars.  The  great 
plain  of  the  Tigris  and 
Euphrates  was  the  gath- 
ering ground  and  bat- 
tlefield of  vast  ancient 
monarchies.  The  plains 
of  the  Po  have  been  the 
arena  in  which  embat- 
tled Europe  has  settled 
some  of  its  deadliest  strifes,  while  the  level  lands  of  Bel- 
gium have  been  dyed  again  and  again  with  the  blood  of 
thousands  and  thousands  of  Europe's  bravest  sons. 

Summary.  —  Level  areas  are  called  plains  when  low, 
plateaus  when  high.  When  a  coast  has  been  elevated 
and  part  of  the  continental  shelf  becomes  exposed,  this  is 
called  a  coastal  plain,  as  the  east  coast  of  the  United 
States  from  New  York  to  the  Gulf  of  Mexico. 

Coastal  plains  have  little  mining  and  manufacturing ; 
their  agricultural  products  vary.  Their  large  cities  lie 
either  at  tide  water  or  at  \\\Q  fall  line  of  the  rivers.  The 
best  drinking  water  on  coastal  plains  usually  comes  from 
artesian  wells. 

Besides  coastal  plains  there  are  lake  plains,  like  those  of 
northern  New  York  and  eastern  North  Dakota,  and 
river  plains,  of  which  the  Mississippi  is  the  best  example. 
The  prairies  have  a  dry,  rich,  treeless,  fertile  soil,  a  result 
of  ancient  glaciation.  The  great  plains  of  the  United 
States  have  an  irregular  surface  usually  barren  of  trees. 


408  .FIRST   YEAR   SCIENCE 


QUESTIONS 

How  does  the  drainage  of  a  coastal  plain  develop? 

What  kind  of  a  shore  line  will  a  coastal  plain  have  ? 

What  are  the  usual  industries  of  a  coastal  plain  ? 

Where  are  the  largest  cities  on  a  coastal  plain  situated  ? 

Describe  the  kind  of  coast  line  that  results  from  the  depression  of 
a  dissected  coastal  plain. 

In  what  way  are  lake  plains  formed  ? 

How  are  river  plains  formed  ? 

What  natural  conditions  made  its  possible  for  the  pioneer  settlers 
to  become  quickly  prosperous  on  the  prairies  ? 

How  have  plains  affected  the  welfare  of  their  inhabitants? 

How  have  plains  influenced  history? 


CHAPTER   XIII 
THE  HIGH  AREAS   OF  THE  EAETH 

190.  Young  Plateaus.  —  Sometimes  large  areas  of  hori- 
zontal rock  are  elevated  high  above  the  sea,  forming  lofty 
plains  whose  surfaces  are  often  irregular,  owing  to  pre- 
vious erosion.  Such  areas  are  called  plateaus.  The  de- 
scent from  a  plateau  to  the  lower  land  is  usually  steep. 
Areas  of  this  kind,  where  streams  are  present,  suffer 
rapid  and  deep  erosion,  since  the  grades  of  the  streams 
are  steep  because  of  the  elevation. 

If  there  is  not  much  rain  there  will  be  few  streams,  and 
these  will  have  deep  and  steep-sided  troughs.  Such  troughs 
render  the  area  very  difficult  to  cross.  The  valleys  are  too 
narrow  for  habitation  or  for  building  roads,  and  the  deep 
troughs  of  the  streams  are  too  wide  to  bridge.  Thus 
the  uplands  are  isolated. 

If  these  high  areas  are  in  a  warm  latitude,  they  are  desir- 
able for  habitation  on  account  of  their  cool  climate,  due  to 
the  elevation  ;  but  if  in  temperate  latitudes,  their  bleak 
surfaces  are  too  cold. 

As  the  river  troughs  wear  back,  the  harder  rocks  stand 
out  like  huge  benches  winding  along  the  course  of  the 
rivers.  From  the  different  benches  slopes  formed  from 
the  crumbling  of  the  softer  strata  slant  backward.  Thus 
the  general  outline  of  the  stream  sides  will  be  something 
like  that  of  a  flight  of  stairs  upon  which  a  carpet  has  been 
loosely  laid. 

An  excellent  example  of  a  region  of  this  kind  which 

409 


410 


FIRST   YEAR   SCIENCE 


has  been  eroded  by  a  strong  river  gaining  its  water  from 
a  distant  region  is  that  of  the  Colorado  Canon  Plateau. 
Here  is  found  the  grandest  example  of  erosion  on  the  face 


COLORADO  PLATEAU. 
The  river  has  cut  a  deep  canon  through  the  plateau. 

of  the  earth.  The  rocks  are  of  various  colors,  and  the 
gorge  is  nearly  a  mile  deep  and  in  places  some  fifteen 
miles  in  width.  Words  are  inadequate  to  express  the 


DISSECTED  PLATEAUS  411 

grandeur  of  the  panorama  spread  out  before  one  who  is 
permitted  to  see  this  gigantic  exhibition  of  the  results  of 
erosion.  Wonderful,  grand,  sublime,  are  mere  sounds 
which  lose  themselves  in  the  ears  of  one  who  looks  out 
upon  this  overpowering  display  of  Nature's  handiwork. 

The  region  is  very  dry,  and  the 'river  receives  few  and 
short  branches  for  many  miles  of  its  course.  The  valley 
is  widening  much  more  slowly  than  it  would  if  this  were 
a  land  of  considerable  rainfall,  and  as  yet  the  river  fills 
the  entire  bottom  of  the  gorge.  The  valley  is  in  the 
early  stages  of  its  development  and  has  just  begun  the 
vast  work  of  wearing  down  the  region.  The  side  streams 
are  small  and  the  interstream  spaces  broad. 

191.  Dissected  Plateaus. — If  a  plateau  has  been  elevated 
for  considerable  time  in  a  region  of  abundant  rainfall,  the 
streams  extend  their  courses  in  networks,  thoroughly  dis- 
secting the  area  and  leaving  between  their  courses  only 
narrow  remnants  of  the  upland.  The  valleys  are  still 
deep,  but  the  intervening  uplands  are  of  small  extent. 
Traveling  over  the  region  in  any  direction  except  along 
the  stream  courses  is  a  continual  process  of  climbing  out 
of  and  into  valleys. 

There  is  very  little  level  space  that  can  be  used  for  cul- 
tivation, and  on  account  of  the  steepness  of  the  slopes  it 
is  very  hard  to  build  roads.  The  river  valleys  are  so 
narrow  that  unless  the  roads  are  perched  high  up  on  the 
sides,  they  are  liable  to  be  swept  away  at  the  time  of 
flood.  Farming  in  these  regions  is  very  discouraging 
because  of  the  difficulty  of  transporting  crops  and  of  find- 
ing anything  but  a  steep  side  hill  on  which  to  grow  them. 

Railroads  can  get  through  only  by  following  the  princi- 
pal valleys,  and  here,  on  account  of  the  narrowness,  the 
engineering  of  the  roads  is  difficult.  Unless  the  region  is 
rich  in  minerals,  it  can  support  only  a  small  population, 


412 


FIRST   YEAR   SCIENCE 


THE  ENCHANTED  MESA. 
With  old  Indian  village  in  the  foreground. 

and  that  will  of  necessity  be  poor.  As  soon  as  the  forests 
are  cut  off,  the  soil  rapidly  washes  down  the  hillsides  and 
leaves  naught  but  bare  surfaces.  Regions  of  this  kind 


A   BUTTE. 


OLD  PLATEAUS 


413 


are  found  in  the  Allegheny  and  Cumberland  plateaus,  ex- 
tending from  New  York  to  Alabama. 

192.  Old  Plateaus.  —  If  a  plateau  remains  elevated  for  a 
great  length  of  time,  the  dissecting  rivers  are  able  to  widen 
their  valleys  and  wear  away  all  the  interstream  spaces, 
except  where  these  are  very  broad.  Thus  the  rivers  bring 


AN  INDIAN  HOGAN. 

the  surface  down  to  a  comparatively  low  level,  with  here 
and  there  a  remnant  which  has  not  been  worn  away,  but 
which  shows  in  its  steep  sides  the  edges  of  the  rock  layers 
which  formerly  spread  over  the  whole  region.  If  these 
residual  masses  are  large,  they  are  called  by  the  Spanish 
name  mesas,  meaning  tables,  and  if  small,  buttes,  from  the 
French  word  which  means  landmarks. 

Some  of  these  mesas  are  so  high  and  so  steep  that  it  is 
impossible  to  climb  them,  and  others  are  simply  low,  flat- 
topped  hills.  A  traveler  in  New  Mexico  and  Arizona 
will  see  many  of  these  mesas,  which,  like  the  lonely  Indian 


414  FIRST   YEAR   SCIENCE 

huts  or  hogans,  are  but  scattered  remnants  of  what  was 
formerly  widespread. 

On  old  plateaus  travel  is  easy.  There  are  no  deep 
valleys,  and  one  can  easily  pass  around  the  mesas,  which  only 
add  charm  to  what  would  otherwise  be  a  most  monotonous 
landscape.  When  these  mesas  are  high,  they  are  some- 
times occupied  by  a  few  Indian  tribes  who  have  fled  to 


CLIFF  DWELLINGS. 
A  protected  retreat  in  a  mesa. 

them  for  protection,  as  the  medieval  barons  when  hard 
pressed  fled  to  their  isolated  castles. 

193.  Broken  Plateaus.  —  The  force  which  has  uplifted  the 
plateaus  is  not  always  uniform  enough  in  its  action  to  lift 
large  areas  without  fracturing  the  rock  layers.  Thus 
plateaus  are  found  which  have  the  rock  layers  broken  and 
displaced.  The  layers  on  one  side  of  the  break  may  stand 
thousands  of  feet  higher  than  those  on  the  other  side. 

This  is  seen  in  the  region  of  the  Grand  Canon  of  the 
Colorado,  where  the  Kaibab  Plateau  stands  about  2000 


HILLS  AND  MOUNTAINS 


415 


feet  above  the  Colorado  Plateau  and  steep  cliffs  bound 
it  on  both  its  east  and  west  sides.  These  fault  cliff's, 
as  they  are  called,  are  found  at  several  other  places  in  this 
region,  showing  that  the  whole  area  was  much  broken  when 
it  was  uplifted.  The  Kaibab  Plateau  itself  is  so  much 
higher  than  the  plateaus  on  either  side  that  it  intercepts 
sufficient  rainfall  to  support  forests,  whereas  the  plateaus 

about     it    are    almost      , . 

barren  of  trees. 

In  the  walls  of  the 
Colorado  Canon  some 
of  these  great  breakage 
lines  can  be  traced  and 
the  same  strata  seen  to 
be  thousands  of  feet 
higher  on  one  side  of 
the  line  than  on  the 
other.  In  front  of  these 
breakage  cliffs  or  fault 
cliffs,  accumulations  of 
debris  extend  along  the 
entire  distance,  show-  A  FAULT- 

ing  that  since  the  uplift  there  has  been  time  for  much 
erosion  even  in  this  dry  region.  The  Colorado  River 
passes  over  these  great  faults  regardless  of  their  existence. 
The  canons  in  the  region  seem  not  to  have  been  influ- 
enced by  the  faulting.  Probably  it  took  place  too  slowly. 

194.  Hills  and  Mountains.  —  Irregular  elevations  of  the 
earth's  surface  are  called  kills,  or  mountains  when  they  are 
of  considerable  height.  In  the  general  use  of  these  terms 
there  is  no  exact  line  of  separation.  Elevations  which  in 
mountain  regions  would  be  called  hills  would  in  a  flat  region 
be  called  mountains.  As  a  rule,  elevations  are  not  termed 
mountains  unless  they  are  at  least  2000  feet  high.  But  if 


416 


FIRST   YEAR   SCIENCE 


the  general  elevation  of  the  country  is  great,  as  in  the 
lofty  regions  of  the  Rockies,  an  elevation  to  be  termed  a 
mountain  must  rise  to  a  striking  height'  above  the  gener- 
ally elevated  surface,  which  is  itself  nearly  everywhere 
more  than  4000  feet  above  the  sea. 

195.  Structure  of  Mountains.  —  Mountains  are  the  results 
of  deformations  in  the  earth's  crust,  due  to  causes  not 
fully  understood  and  the  study  of  which  is  a  part  of  geology. 


APPALACHIAN  PLATEAU. 
A  range  of  old  mountains  greatly  reduced  in  height. 

The  crust  of  the  earth  has  been  folded,  pushed  up,  crumpled 
and  in  many  ways  distorted  so  that  some  portions  have 
been  elevated  to  a  considerable  height  above  sea  level. 
Where  these  elevated  portions  have  not  remained  long 
enough  to  be  worn  down,  they  form  mountains. 

All  lofty  mountains  have  been  elevated  in  comparatively 
recent  geological  time,  but  this  of  course  means  millions 
of  years  ago.  If  mountains  now  lofty  were  geologically 


BLOCK  MOUNTAINS  417 

old,  they  would  long  ago  have  been  worn  down.  The  older 
mountains  of  the  earth  are  all  comparatively  low,  not 
because  they  were  never  elevated  as  high  as  the  lofty 
mountains  of  to-day,  but  because  their  greater  age  has 
longer  subjected  them  to  erosion  and  thus  reduced  their 
height. 

It  is  difficult  to  classify  the  different  kinds  of  mountains, 
for  very  few  of  them  are  simple  in  their  structure,  but 
certain  kinds  of  mountain  forms  are  easily  distinguished. 

196.  Block  Mountains.  —  Experiment  131.  —  Take  three  pieces 
of  smooth,  straight-edged  boards,  two  of  which  are  about  15x55  cm. 
on  a  side  and  the  other  8x  55.  Place  these  flat  on  a  table  with  the 
smaller  board  in  the  middle  and  the  longer  edges  close  together. 
Sift  corn  meal,  fine  coal  dust,  powdered  pumice,  plaster  of  Paris  and 
fine  sawdust  in  even  layers  over  the  boards.  Now  lift  carefully  the 
inner  edge  of  one  of  the  wider  boards  and  slip  under  it  a  narrow  strip 
of  wood  1  or  2  cm.  thick.  The  layers  of  material  spread  over  the 
boards  will  be  broken  and  slant  back  from  the  line  of  breakage  with 
their  edges  exposed  along  this  line.  Do  the  same  with  the  wide 
board  on  the  other  side.  The  conditions  shown  will  be  similar  to 
those  exhibited  in  block  mountains. 

In  southern  Oregon  and  extending  southward  are  found 
long,  narrow  mountain  ridges,  having  a  steep  cliff  on  one 
side  and  a  gentle  slope  on  the  other.  Between  these 
ridges  are  flat,  troughlike  depressions  in  which  small  lakes 
are  sometimes  found.  The  ridges  are  formed  of  thick 
layers  of  rock  inclined  at  the  same  angle  as  the  long  slope 
of  the  ridge.  The  short  slope  of  the  ridge  exposes  the 
edges  of  these  layers  which  have  been  broken  across. 

The  debris  slopes  at  the  foot  of  the  steep  cliffs  in  some 
cases  are  slightly  broken  across  in  a  direction  parallel  to 
the  cliff.  The  steep  cliffs  sometimes  face  each  other  with 
a  somewhat  flat  depression  between,  and  sometimes  the 
cliff  on  one  ridge  faces  the  long  slope  of  the  next.  Some 


418  .FIRST   YEAR   SCIENCE 

'  '  i* 

of  the  ridges  are  more  gullied  than  others,  showing  longer 
exposure  to  erosion. 

These  ridges  are  due  to  strains  which  have  broken  the 
rock  layers  and  elevated  those  on  one  side  of  the  fracture 
above  those  on  the  other  side,  so  that  a  steep  fracture 
cliff  has  been  formed  with  the  rock  layers  slanting  back- 
ward from  its  elevated  edge.  (Fig.  118.)  Mountains  of 
this  kind  are  called  block  mountains.  As  is  seen  from  the 
fracturing  of  the  debris  slopes,  the  movement  of  elevation 
is  not  yet  completed. 


Fig.   1 1 8. 

As  some  of  the  ridges  are  more  gullied  than  others,  it 
appears  that  the  fracturing  did  not  take  place  all  at  one 
time,  but  that  the  more  gullied  ridges  were  formed  first. 
Earthquakes  are  not  uncommon  in  this  region.  These  are 
caused  by  a  small  slipping  along  the  fault  line. 

In  Oregon  these  ridges  are  little  eroded.  They  are 
simple  in  structure  and  young  in  age.  The  longer  streams 
flow  down  the  gentle  slopes  parallel  to  the  surface  of  the 
rock  layers  and  the  shorter  streams  along  the  steeper 
slopes  across  the  edges  of  the  layers. 

197.  Folded  Mountains.  —  Experiment  132.  —  To  the  long  edge  of 
a  piece  of  board  about  10  cm.  wide  and  20  cm.  long  tack  securely  one 
of  the  shorter  edges  of  a  piece  of  rather  thick  rubber  dam  about  20 
x  25  cm.  Tack  the  opposite  edge  to  a  strip  of  board  about  2  cm. 
wide  and  20  cm.  long.  Place  the  rubber  dam  thus  arranged  on  a  smooth 
table  and  secure  the  wide  board  firmly  to  the  table  by  a  clamp  or  nail. 


FOLDED  MOUNTAINS  419 

Taking  hold  of  the  strip,  stretch  the  rubber  dam  as  much  as  it  will 
readily  stand.  Fasten  the  strip  so  as  to  hold  the  rubber  dam  in  this 
stretched  position. 

Sift  fine  sawdust,  plaster  of  Paris,  fine  coal  dust,  ground  pumice, 
corn  meal,  or  any  other  distinctly  colored  substances  in  even  layers 
over  the  stretched  rubber  dam.  Slightly  dampen  the  layers.  Re- 
leasing the  strip,  allow  the  rubber  dam  to  contract  very  slowly.  When 
it  has  fully  contracted,  cut  carefully  through  the  layers  of  material 
with  a  thin  knife  and  remove  that  which  is  on  one  side  of  the  cut. 
The  layers  will  have  been  folded  into  irregular  undulating  folds,  thus 
simulating  folded  mountains. 

Where  layers  of  rock  are  subjected  to  slow,  uniform 
and  tremendous  lateral  pressure,  they  may  form  undulat- 


Fig.   119. 

ing  folds  with  little  fracturing.  (Fig.  119.)  The  contract- 
ing of  the  interior  of  the  earth,  due  to  cooling,  has  some- 
times brought  to  bear  such  pressure,  and  in  a  few  cases 
undulating  folds  have  been  produced. 

The  best  example  of  this  folding  is  that  of  the  Jura 
Mountains,  between  Switzerland  and  France.  Here  the 
almost  regular  folding  of  the  strata  can  be  seen  wherever 
the  streams  have  cut  across  the  mountains.  The  moun- 
tains are  so  young  that  there  has  been  little  carving. by 
erosion  and  the  downfolds  still  form  the  valleys  and  the 
upfolds  the  ridges. 

The  rock  layers  composing  these  folds  contain  marine 
fossils,  showing  that  they  were  once  horizontal  and  must 
have  been  formed  in  the  sea.  The  longer  streams  run 
down  the  troughs  of  the  folds,  but  in  some  places,  often 


420  FIRST   YEAR    SCIENCE 

'  .  .^ 

where  the  folds  are  least  high,  streams  cut  across  them 
and  pass  from  one  trough  to  another.  Along  these  trans- 
verse stream  courses  are  usually  built  the  roads  that  cross 
the  ridges. 

Sometimes  the  tops  of  the  ridges  have  been  sufficiently 
worn  away  or  are  broad  enough  to  form  considerable  flat 
areas,  where  little  villages  are  situated.  But  most  of  the 
population  is  found  along  the  longitudinal  valleys,  espe- 


FOLDED  STRATA. 

cially  where  there  are  cross  valleys.  Some  of  the  cross 
streams  seem  to  have  no  connection  with  sags  in  the  folds, 
but  appear  to  have  cut  their  valleys  through  the  folds  as 
fast  as  they  rose,  thus  indicating  that  the  rate  of  folding 
was  slow. 

198.  Massive  Mountains.  —  The  mountains  already  studied 
are  all  comparatively  low.  Probably  none  of  them  rises  to 
a  height  exceeding  6000  feet.  They  are  simple  in  form 


MASSIVE  MOUNTAINS  421 

and  outline,  and  although  pleasing  features  in  the  land- 
scape, are  a  bit  monotonous.  Massive  mountains,  on  the 
contrary,  are  varied  in  form,  lofty  in  height  and  are  among 
the  grandest  and  most  inspiring  of  Nature's  marvels. 

In  all  ages  mountains  have  been  an  inspiration  to  man's 
nobler  thoughts  and  higher  aspirations.  With  their  heads 
piercing  the  azure  vault  of  heaven  and  towering  with 


MASSIVE  MOUNTAINS. 
The  high  Sierras. 

gigantic  mass  above  the  lower  world,  they  force  man  to 
look  up,  and  in  the  contemplation  of  their  nobility  to  for- 
get his  meaner  self.  Like  everything  else  which  holds 
enduring  admiration,  these  are  the  result  of  strain  and 
stress  and  never  ceasing  battle  with  the  forces  of  destruc- 
tion. 

The  structure  of  massive  mountains  is  complex  in  the 
extreme.  Rock  layers  are  often  folded,  twisted  and  con- 
torted (Fig.  120)  beyond  all  recognition  of  their  initial 


422  FIRST   YEAR   SCIENCE 

'  '  v* 

condition.  Their  uplift  has  been  no  simple  process,  each 
age  has  added  its  peculiar  impulse  to  their  growth.  As 
the  forces  of  elevation  have  been  lifting -them  up,  those  of 
degradation  have  been  cutting  them  down.  Their  broad 
brows  have  been  carved  into  peaks  and  pinnacles,  and 
gorges  and  caverns  have  been  cut  into  their  flanks. 

The  different  rock  masses  which  enter  into  their  struc- 
ture have  each  assumed  its  own  peculiar  lineaments  under 
the  carving  of  the  wind,  rain,  streams,  avalanches  and 
glaciers,  and  thus  the  variegated  beauty  of  the  whole  mass 
has  been  produced.  The  central  part  of  massive  moun- 
tains is  composed  of  igneous  rocks,  but  on  the  sides  over- 


Fig.  120. 

lying  these,  sedimentary  rocks  are  found.  The  Rockies, 
the  Alps  and  the  Himalaya  Mountains  are  of  this  kind. 

199.  Mountains  that  no  longer  Exist.  —  The  mountains 
which  are  now  such  prominent  features  of  the  earth's  sur- 
face are  neither  all  the  same  age  nor  are  they  the  only 
representatives  of  this  kind  of  land  forms  that  have  ever 
existed.  All  the  kinds  of  mountains  thus  far  considered 
are  young  in  geological  age,  although  some  are  older  than 
others. 

All  parts  of  the  earth's  surface  are  being  gradually  worn 
down  by  the  action  of  water,  but  the  higher  portions  are 
worn  more  rapidly  than  those  lower,  as  here  the  forces  of 
denudation  act  more  intensely.  Thus  if  mountains  stop 
growing,  they  decrease  in  height  until  finally  they  are  too 
small  to  be  called  mountains.  Their  rocks  will  be  crumpled 


MOUNTAINS   THAT  NO  LONGER   EXIST  423 

and  folded,  and  all  the  characteristics  of  mountain  form 
will  be  present  except  the  elevation. 

The  slant  of  the  rock  layers  may  be  such  as  to  indicate 
a  great  elevation  in  former  times,  but  now  only  the  roots 
of  the  mountains  are  left  and  the  region  is  of  very  moder- 
ate elevation.  Regions  of  this  kind  are  found  in  many 
parts  of  the  earth. 

In  the  Appalachian  highlands  of  Pennsylvania  the 
rocks  show  that  they  were  once  folded  into  ridges  and 
troughs  something  like  those  of  the  Jura.  But  now  the 

arches  have  been  worn     

away,  and  the  existing 
ridges  are  due  to  the 
resistance  which  the 
harder  layers  offer  to 
erosion.  These  ridges 
are  as  likely  to  occur 
where  formerly  the 

troughs    of     the    folds 

BEN  NEVIS. 

were   as    m  what   were     A  mountain  much  worn  down  but  still  high, 
the  crests. 

The  configuration  of  the  country  is  not  at  all  as  it  was 
when  the  rocks  were  folded.  The  elevation  then  .  was 
much  greater  than  the  highest  ridges  at  present.  If  the 
beds  should  be  reconstructed  as  they  now  lie,  they  would 
indicate  a  height  much  greater  than  the  mountains  ever 
had  at  any  time.  This  indicates  that  these  mountains 
have  been  lifted  up  and  worn  down  more  than  once. 

Another  region  in  which  the  mountains  have  been  re- 
duced to  inconspicuous  heights  is  the'Laurentian  Plateau, 
the  area  around  Hudson  Bay.  These  mountains  were 
very  ancient  and  were  worn  down  long,  long  ago.  In 
some  regions  like  southern  New  England,  as  the  mountain 
structure  has  been  worn  down,  it  has  left  here  and  there 


424 


..FIRST   YEAR   SCIENCE 


a   residual   height  like    Mt.    Monadnock   which   has   not 
been  fully  reduced. 

Although  the  general  features  of  su-ch  a  country  are 
those  of  hills  and  valleys  and  it  has  little  of  the  appear- 
ance of  a  plain  as  one  passes  over  it,  yet  it  will  be  found 
that  the  uplands  have  a  general  uniformity  of  elevation. 
Such  an  area  is  called  a  peneplain.  The  residual  mountains 


THE  MATTERHOBN. 

which  rise  above  the  general  level  of  the  country  and  of 
which  Monadnock  is  a  sample  have  been  named  monadnocks. 
This  is  simply  a  name  for  a  mountain  left  above  a  region 
which  has  been  cut  down  by  erosion  to  an  irregular  plain. 
200.  Mountain  Peaks.  —  In  mountain  regions  the  features 
which  are  often  most  impressive  are  the  serrated  peaks 
which  rise  above  the  main  mass  of  the  mountains.  The 
shapes  of  these  peaks  vary  greatly  in  different  mountain 
regions  and  tend  to  give  individuality  to  the  mountains. 


EARTHQUAKES  425 

The  peaks  have  been  formed  by  erosion,  and  their  pecul- 
iarities are  due  to  the  different  kinds  and  positions  of  the 
rocks  from  which  they  have  been  carved. 

The  younger  mountains  which  have  not  been  subjected 
to  erosion  for  a  long  time  do  not  show  the  peak  and  ridge 
structure.  Their  personal  characteristics  have  not  had 
time  enough  yet  to  assert  themselves.  All  these  peaks 
are  the  result,  not  only  of  original  uplift,  but  of  subsequent 
carving. 


THE  TBTON  RANGE. 

201.  Mountain  Ranges.  —  As  a  rule  mountains  are  found 
in  ranges.     The  mountains  in  the  range  are  by  no  means 
all  the  same  elevation,  nor  is  the  range  necessarily  contin- 
uous, there  being  often  gaps  along  its  course.     Neither 
were  all  ranges  in  a  mountain  region  elevated  at  the  same 
time.     Those  which  make  up  the  mountain  region  of  the 
western  United  States  differ  much  in  the  time  of  their 
elevation. 

202.  Earthquakes.  —  In    mountain    regions    which    are 
young  or  still  growing,  earthquakes  are  not  uncommon. 
These  are  due  to  breaks  or  slips  of  a  few  inches  or  a  few 
feet  in  the  rock  structure.     From  the  place  at  which  the 
break  or  slip  takes  place  the  motion  is  transmitted  through 


426 


.FIRST   TEAR   SCIENCE 


the   rock  mass   to  the   surface,   where  it  causes  sudden 

and  often  tremendous 
shocks.  These  slippings 
may  occur  occasionally 
for  ages  along  the  same 
fault  line.  Sometimes 
they  are  intense  enough 
to  cause  great  damage  ; 
at  other  times  only  a 
slight  tremor  is  felt. 

The  rapidity  of  the 
transmission  of  the 
shock  differs  with  the 
kind  of  material  through 
which  it  is  transmitted, 
varying  from  a  few 
hundred  feet  to  several 

thousand  feet  per  second.  The  nearer  a  place  is  to  the 
break  or  slip  the  greater 
is  the  intensity  of  the 
shock.  Sometimes  the 
crack  or  fault  along 
which  the  movement 
occurs  reaches  to  the 
surface  and  makes  the 
displacement  apparent. 

If  an  earthquake  orig- 
inates under  the  sea,  a 
great  wave  may  be  de- 
veloped which  rushes 
inland  from  the  coast, 
causing  great  destruc- 
tion. One  of  the  most 
fearful  of  these  waves  occurred  at  Lisbon,  Portugal,  in 


FENCE    BROKEN    BY    SLIPPING   OF   THE 
EARTH  ALONG  A  FAULT  LINE. 


EARTHQUAKES 


427 


THE  RESULT  OF  AN  EARTHQUAKE. 


PLACER  MINING  IN  THE  SIERRAS. 
The  sand  is  washed  from  the  gold  by  huge  streams  of  water. 


428 


FIRST   YEAR   SCIENCE 


1755,  sweeping  away  thousands  of  people  who  had  rushed 
into  an  open  part  of  the  city  to  get  away  from  the  falling 
buildings  caused  by  the  earthquake  shoek. 

Sometimes  earthquakes  are  followed  by  terrible  fires 
which  cannot  be  extinguished  on  account  of  the  disarrange- 
ment of  the  water  supply.  This  was  the  case  in  the  San 
Francisco  earthquake. 

203.  Products  of  Mountain  Regions.  —  When  rocks  are 
folded  and  crushed,  in  forming  mountains,  heat  is  gener- 
ated, and  heated  water 
under  pressure  acts  upon 
the  components  of  the 
rocks  and  dissolves  some 
of  their  minerals,  which 
accumulate  in  cracks 
and  crevices  called  veins. 
When  the  overlying 
beds  have  been  worn 
away,  these  mineral 
veins,  formed  deep  be- 
low the  surface,  are  ex- 
posed and  can  be  mined. 
Mountains  are  therefore 
the  great  mining  re- 
gions. 


DEEP 


DOWN     IN     THE     CALUMET 

HECLA  MINE. 
The  world's  greatest  copper  mine. 


AND 


In  this  country  min- 
ing is  a  most  important 
industry  in  the  Sierra 
Nevada  Mountains  and  in  the  Appalachian  region. 
In  one  are  found  great  quantities  of  copper,  silver 
and  gold,  and  in  the  other  iron  and  coal.  In  the  old 
Laurentian  Mountain  region,  near  the  Great  Lakes,  much 
copper  is  found.  The  Alps  and  the  Pyrenees  are  among 
those  mountains  that  have  few  minerals. 


EFFECT  OF  MOUNTAINS   ON  CLIMATE 


429 


If  mountains  are  not  too  high,  they  are  also  regions  of 
forests  and  furnish  great  quantities  of  lumber.  The  sur- 
face is  so  rough  that  agriculture  is  not  easily  carried  on, 
but  they  have  great  areas  of  pasture  which  often  support 
large  herds  of  cattle,  sheep,  and  goats. 

204.  Effect  of  Mountains  on  Climate.  —  All  over  the  world 
where  people  have  the  money  and  the  leisure  they  are 
accustomed  to  go  either  to  the  mountains  or  the  seashore 


TOP  OF  PIKE'S  PEAK  IN  SUMMER. 
Notice  the  snow  and  the  rocks  broken  up  by  the  freezing  water. 

in  summer  in  order  to  get  where  it  is  cooler.  They  might 
for  the  same  purpose  travel  northward  in  the  northern 
hemisphere,  but  they  would  need  to  go  many  times  as  far 
to  get  the  same  fall  of  temperature. 

In  summer  one  must  ascend  a  mountain  on  an  average 
about  300  feet  vertically  to  get  a  mean  fall  of  1°  F., 
whereas  one  must  travel  over  60  miles  north  to  get  the 
same  change.  In  winter  one  must  ascend  farther  on  the 
mountain  and  travel  not  so  far  north,  to  get  a  change  of  a 
degree.  As  one  ascends  a  mountain  it  grows  colder  and 
colder.  In  ascending  a  high  mountain  in  the  tropics  one 


430  FIRST   YEAR   SCIENCE 

'  '  *«* 

passes  through  all  the  changes  in  climate  which  one  would 
pass  in  going  from  the  equator  toward  the  poles. 

As  already  stated,  high  mountains  also  affect  the  climate 
of  the  country  near  them.  The  windward  side  of  moun- 
tains is  moist,  since  the  moisture  in  the  air  is  condensed  in 
rising  over  them.  On  the  lee  side  the  country  is  dry,  as 
the  air  which  moves  over  it  has  already  been  deprived  of 
its  moisture. 


POPOCATEPETL. 
A  snow-covered  mountain  in  the  tropics. 

The  country  on  the  lee  side  will  also  be  subject  to  hot, 
dry  winds  like  the  chinook  winds  of  the  eastern  Rockies 
and  the  foehn  in  Switzerland.  As  the  moist  winds  pass 
over  the  mountains  their  moisture  is  condensed.  This 
raises  their  temperature  so  that  it  is  above  what  it  would 
normally  be  at  the  altitude  reached.  As  they  come  down 
on  the  lee  side  of  the  mountain,  the  air  is  compressed  and 
thus  heated  so  that  on  this  side  it  is  considerably  warmer 


AVALANCHES  431 

at  the  same  altitude  than  on  the  windward  side.  Thus 
high  mountains  affect  not  only  the  rainfall,  but  the  tem- 
perature changes  of  the  region  round  about. 

205.  Avalanches.  —  In  mountain  regions  where  the  in- 
clination of  the  surface  is  steep,  the  loose  material  is  liable 
to  slide  down  the  mountain  sides,  especially  when  it  becomes 
moist  because  of  long  rains,  or  of  the  thawing  of  the  frozen 
ground.  As  the  material  slides,  the  quantity  increases, 


LANDSLIDE. 
Covering  one  of  the  main  roads  of  Norway. 

arid  momentum  or  force  of  movement  is  gained  until  a 
vast  mass  sweeps  with  almost  irresistible  force  down  the 
side,  wrenching  away  trees,  bowlders  and  whatever  lies  in 
its  path.  On  reaching  the  valley  the  debris  is  piled  in 
irregular  mounds. 

The  scars  of  these  avalanches  are  seen  on  the  sides  of 
almost  all  high  mountains.  In  mountain  regions  which 
are  inhabited,  avalanches  are  frequently  very  destructive 
of  life  and  property.  In  the  Alps  large  forests  are  often 


432 


FIRST   YEAR   SCIENCE 


maintained  above  villages  to  check  the  avalanches  if  pos- 
sible and  thus  to  protect  the  villages. 

206.   Mountain  Animals  and  Plants.  —  A*s  the  temperature 
of  mountains   varies  greatly  from  bottom  to  top,  so  the 

animals  and  plants  must 

vary.  Near  the  foot  of 
the  mountain  the  plants 
will  be  similar  to  those 
of  the  surrounding 
country,  but  these  will 
soon  disappear  as  the 
slope  is  ascended,  since 
the  temperature  will 
have  decreased,  and 
their  place  will  be  filled 
by  those  capable  of  with- 
standing greater  cold. 
If  the  mountains  are 
sufficiently  high,  the 
tops  will  be  bare  or 
covered  with  ice  and 


LANDSLIDE  AT  AMALFI. 

This  destroyed   a  part  of  the  famous 

monastery. 


snow. 

The  animals  of  moun- 
tains vary  somewhat  as 
do  the  plants,  but  since  animals  have  the  power  of  move- 
ment, their  distribution  will  not  be  so  uniform.  They 
may  ascend  the  mountain  during  the  summer  and  retreat 
down  the  slope  when  the  weather  becomes  severe.  Animals 
driven  from  the  plains  by  other  animals  or  by  man  often 
find  a  place  of  safety  in  mountain  regions. 

The  buffalo  of  the  western  United  States  found  their 
only  place  of  safety,  until  protected  by  stringent  laws,  in 
the  mountainous  region  of  the  Yellowstone.  The  last 
small  herd  of  caribou  made  their  final  stand  in  central 


MOUNTAIN  PEOPLES 


433 


Maine  on  the  heights  of  Mt.  Katahdin  ;  the  deer  which 
once  roamed  widely  over  New  York  State  now  are  re- 
stricted to  the  Adiron- 
dack Mountains.  In 
these  mountainous  re- 
treats pursuit  is  diffi- 
cult, and  they  can  per- 
sist for  a  long  time  after 
being  exterminated  else- 
where. 

Some  animals,  such  as 
the  chamois  of  the  Alps  Ro(,KY  MouNTAIN  GoATS. 

and  the  mountain  goat 

of  the  Rockies,  are  particularly  adapted  to  mountain  life 
and  find  a  congenial  habitat  nowhere  else. 

207.  Mountain  Peoples.  —  Mountains  offer  a  retreat  to 
persecuted  people  as  well  as  to  animals.  Here  are  often 
found  the  races  which  once  inhabited  the  surrounding 
plains,  but  which  have  been  driven  from  them  by  conquer- 
ors. The  people  of  Wales  and  the  Scotch  highlanders 
are  probably  descendants  from  more  ancient  inhabitants 
of  the  island  than  those  in  control  to-day.  The  Pyrenees, 
the  Caucasus  and  the  Himalaya  Mountains  each  contain 
tribes  which  were  driven  from  the  lower  plains,  but  have 
been  able  in  these  retreats  to  withstand  invaders  who 
were  too  powerful  for  them  in  their  former  homes. 

Flocks  and  herds  frequently  make  up  the  greatest 
wealth  of  mountain  peoples.  Indeed  in  these  regions  it  is 
common  to  reckon  a  man's  wealth  by  the  number  of  cows 
he  can  keep.  In  summer  the  cattle  are  driven  to  the 
higher  slopes  of  the  mountains,  called  alps  in  Switzerland 
and  saeters  in  Norway.  In  winter  they  are  brought  down 
to  the  valleys,  where  the  little  villages  are,  and  where 
every  available  foot  of  land  has  been  utilized  to  produce 


434  ..FIRST  TSAR   SCIENCE 

hay  for  their  feeding  during  the  long  winter  months. 
Life  is  hard  and  meager,  and  industry,  foresight  and  thrift 
are  necessary. 

As  mountain  valleys  are  separated  from  each  other  by 
ridges  which  for  a  considerable  part  of  the  year  are  al- 
most impassable,  the  inhabitants  are  divided  into  groups 
whose  world  consists  largely  of  the  small  valley  in  which 


A  MOUNTAIN  SHEPHERD  WITH  HIS  FLOOR. 

they  live.  Their  customs  and  manners  of  dress  become 
in  time  somewhat  different  from  those  of  the  valleys  about 
them.  In  Norway  many  of  the  different  valleys  have  de- 
veloped various  unique  and  beautiful  costumes.  Only 
in  recent  years,  since  travel  has  become  more  common, 
have  these  been  laid  aside  for  the  humdrum,  characterless 
costumes  of  the  rest  of  Europe  and  of  the  United  States. 
In  some  of  the  Scotch  Highlands  the  natives  still  cling  to 
their  ancient  dress. 


MOUNTAIN  PEOPLES 


435 


Old-fashioned  customs  still  maintain  their  hold  in 
mountain  regions  long  after  they  have  been  discarded  in 
the  surrounding  country  where  intercommunication  is 
easier.  In  the  southern  Appalachian  Mountains  many  of 
the  customs  of  the  early  pioneers  are  still  common.  Home- 
spun clothing  is  still  manufactured,  and  hog  and  hominy 
are  the  principal  diet. 


. 


A  NEAR  VIEW  OF  THE  JUNGFRAU. 
Such  scenes  as  this  produce  the  wealth  of  Switzerland. 

In  mountain  regions,  such  as  the  northern  Appalachians 
and  Alps,  where  travel  has  been  made  comparatively  easy, 
caring  for  the  summer  tourist  has  become  the  most  impor- 
tant business.  Here  the  old-fashioned  customs  have  been 
laid  aside  and  the  boarding-house  and  hotel  industry  has 
largely  supplanted  all  others.  Such  mountain  regions  have 
become  a  playground  for  the  rest  of  the  world,  and  the 
bracing  air  and  cool  climate  are  as  great  revenue  producers 
as  are  fine  farming  lands  and  water  powers. 


436 


.FIRST   YEAR   SCIENCE 


In  mountain  regions  rich  in  ores,  mining  naturally  be- 
comes the  chief  industry,  and  here,  if  there  were  any 
secluded  native  inhabitants,  these  have*'  been  replaced  by 
the  energetic  miners  from  distant  places.  The  deep  and 
remote  valleys  and  mountain  sides  have  become  the  homes 
of  mining  camps  and  cities.  Railroads  have  been  built 
to  these,  overcoming  almost  impassable  obstructions,  and 


CRIPPLE  CREEK. 
The  largest  mining  camp  in  the  world. 

ore  crushing  and  smelting  works  supply  the  places  of  the 
mills  and  factories  of  the  manufacturing  cities.  When  the 
ore  fails,  the  army  of  workers  moves  on,  and  the  city, 
once  thriving  and  booming,  becomes  suddenly  simply  an 
aggregation  of  empty  dwellings. 

208.  Effect  of  Mountains  on  History.  —  Not  only  have 
mountains  been  retreats  for  the  vanquished,  but  they  have 
been  barriers  against  further  conquest  by  the  conquerors. 
It  is  very  difficult  for  an  army  to  traverse  a  mountain 


EFFECT  OF  MOUNTAINS  ON  HISTORY  437 

range.  For  a  long  time  the  Alps  hemmed  in  the  power 
of  Rome.  One  of  the  greatest  exploits  of  Hannibal  and 
later  of  Napoleon  was  the  passage  of  these  same  mountains. 

In  our  own  country  the  Appalachian  Mountains  acted 
for  a  long  time  as  an  impassable  barrier  to  the  expansion 
of  the  Thirteen  Colonies.  The  trails  across  them  were 
so  long  and  difficult  that  it  was  many  years  before  the  fer- 
tile plains  on  their  western  side  became  populated.  The 
Mohawk  valley  opened  a  comparatively  easy  route  at  the 
north,  but  the  Cumberland  trail  at  the  south  was  long, 
circuitous  and  full  of  places  suitable  for  Indian  ambuscade. 

The  little  mountain  country  of  Switzerland  is  a  buffer 
state  for  the  rest  of  Europe.  Afghanistan,  rough,  moun- 
tainous and  desert,  is  a  buffer  state  for  Asia. 

Mountains  are  often  used  as  boundaries  to  countries,  as 
in  the  case  of  the  Pyrenees  between  France  and  Spain 
and  the  Carpathian  Mountains  between  Austria-Hungary 
and  Roumania.  In  early  times  it  was  thought  sufficient  to 
indicate  the  crest  of  the  mountains  as  the  boundary  line, 
but  soon  it  was  found  that  what  was  to  be  called  the  crest 
was  so  open  to  controversy  that  definite  lines,  accurately 
determined  from  point  to  point,  had  to  be  substituted. 

Sometimes  the  determination  of  what  shall  be  called  the 
crest  line  has  given  rise  to  bitter  international  disputes,  as 
was  the  case  recently  between  Chile  and  Argentina.  It 
may  happen  that  mountain  boundaries  are  so  broad  and 
complicated  that  a  little  country  inserts  itself  along  the 
boundary  of  two  powerful  nations  and  is  able  to  protect 
itself  from  being  absorbed  by  either.  The  little  country 
of  Andorra,  containing  only  150  square  miles,  situated  in  a 
lofty  valley  on  the  southern  slope  of  the  Pyrenees,  with  a 
population  not  exceeding  10,000,  has  remained  independ- 
ent for  nearly  a  thousand  years  in  spite  of  its  powerful 
neighbors. 


438  .  FIRST  YEAR  SCIENCE 

Summary.  —  The  high  parts  of  the  earth  are  plateaus 
and  mountains.  Some  plateaus  are  dissected  by  the 
troughs  of  rivers  that  run  through  them  and  some  are 
broken  by  faults.  When  plateaus  are  old  and  worn  down 
they  usually  shpw  remnants  of  their  former  surface  in 
buttes  and  mesas. 

Mountains  are  elevations  higher  than  hills.  Slock 
mountains  are  formed  by  breaks  in  the  rock  layers  of  the 
earth ;  folded  mountains  are  due  to  folds  caused  by 
lateral  pressure.  Massive  mountains  are  complex  in 
structure  and  their  causes  are  various.  The  peaks  of 
mountains  are  formed  by  erosion.  Many  mountains  are 
found  in  ranges. 

Mountains  have  a  great  effect  upon  climate.  The 
windward  side  of  mountains  is  usually  wet  and  the  lee- 
ward side  dry.  The  wind,  rain,  and  snow  cause  ava- 
lanches, which  often  do  great  harm  to  the  plants  and 
animals  of  the  mountains  and  valleys. 

Mountains  have  also  a  great  effect  upon  history.  Not 
only  do  they  form  excellent  boundaries  between  nations 
and  states,  but  they  offer  protection  to  weak  animals 
which  are  unable  to  withstand  their  stronger  neighbors  in 
the  unprotected  conditions  of  the  plains. 


QUESTIONS 

Describe  the  characteristics  of  a  young  plateau. 

Why  do  not  dissected  plateaus  attract  a  dense  population  ? 

What  are  the  characteristic  features  of  an  old  plateau  ? 

Where  in  the  United  States  are  broken  plateaus  found  ? 

Why  are  there  no  lofty  old  mountains? 

How  are  block  mountains  formed  V  Where  are  mountains  of  this 
kind  found?  How  are  folded  mountains  formed?  Where  is  a  fine 
example  of  such  mountains  to  be  seen  ? 

What  are  the  characteristics  of  massive  mountains? 


SUMMARY  439 

What  happens  to  mountains  if  they  are  exposed  to  erosion  for  a 
very  long  time?  Where  in  the  United  States  are  such  mountains 
found  ? 

What  are  the  causes  which  produce  mountain  peaks  ? 

How  are  earthquakes  caused  ? 

What  are  the  principal  industries  in  mountain  regions  ? 

How  do  mountains  affect  climate  ? 

What  influence  have  mountains  had  upon  plants  and  animals  ? 

What  influence  do  mountains  have  upon  their  human  inhabitants  ? 

What  has  been  the  effect  of  mountains  upon  history.? 


CHAPTER  XIV 


VOLCANOES 

209.  Subsurface  Earth.  —  Many  excavations  and  borings 
have  been  made  deep  into  the  earth's  surface,  and  it  lias 
been  found  that  the  temperature  increases  with  the  depth. 
The  rate  of  increase  is  not  the  same  in  different  places,  nor 


MOUNT  SHASTA. 
An  extinct  volcano. 

is  the  increase  always  uniform  in  the  same  place.  The 
average  of  a  number  of  deep  excavations  in  different  parts 
of  the  earth  gives  a  rise  of  1°  F.  for  each  70  or  80  feet  of 
descent. 

The  greater  the  pressure  to  which  rocks  are  subjected  the 
more  difficult  it  is  to  melt  them.     If  it  were  not  for  this,  the 

440 


MONTE  NUOVO  441 

solid  part  of  the  earth  could  not  be  more  than  40  or  50  miles 
thick,  as  the  interior  heat  would  melt  rocks  under  ordinary 
pressure.  But  the  earth  is  too  rigid  for  its  interior  to  be 
otherwise  than  solid.  So  great  is  the  pressure  to  which  it 
is  subjected  that  probably  none  of  the  material  deep  down 
in  the  interior  of  the  earth  is  in  a  molten  condition. 

If  the  pressure  near  the  surface  should  be  decreased, 
or  if  the  normal  amount  of  heat  at  any  place  should  be 
increased,  the  material  might  become  fused,  and  under 
certain  conditions  might  find  its  way  to  the  surface.  We 
know  that  heated  material  from  below  does  rise  toward  the 
surface  and  intrude  itself  into  the  surface  rocks  and  in 
some  places  pour  forth  over  the  surface. 

What  causes  the  uprising  and  outpouring  of  this  molten 
material  from  below  the  surface  of  the  earth,  and  how  and 
why -it  reaches  the  surface  are  questions  which  as  yet  are 
unanswerable.  But  as  soon  as  this  igneous  material  comes 
within  the  range  of  observation,  its  properties  and  actions 
can  readily  be  studied.  The  following  descriptions  of  some 
well-known  typical  volcanoes  show  some  of  the  results  of 
subsurface  activity. 

210.  Monte  Nuovo.  —  In  1538,  on  the  shore  of  the  Bay 
of  Naples  near  Baise,  that  once  famous  resort  of  the 
Roman  nobles,  after  a  period  of  severe  earthquake  shocks 
there  suddenly  occurred  a  tremendous  eruption.  From 
within  the  earth  emerged  a  mass  of  molten  material  blown 
into  fragments  by  the  explosion  of  the  included  gases. 
Within  a  few  days  there  was  formed  Monte  Nuovo,  a  hill 
440  feet  high  and  half  a  mile  in  diameter,  having  in  the 
top  a  cup-shaped  depression  or  crater  over  400  feet 
deep. 

So  great  was  the  explosive  force  of  this  eruption  that 
none  of  the  ejected  material  was  poured^  out  in  the  form 
of  a  liquid.  The  whole  hill  is  made  up  of  dust,  small 


442 


FIRST  YEAH   SCIENCE 


stones  and  porous  blocks  of  rock  which  resemble  the  slag 
of  a  blast  furnace.  The  small  fragments  in  such  erup- 
tions are  called  ash  or  cinders.  In  a  \Teek  the  eruption 
was  over,  and  nothing  of  the  kind  has  since  occurred  in 
the  region. 

When  visited  by  the  writer  a  few  years  ago,  the  bottom 
of  the  crater  was  a  level  field  planted  to  corn.  The  whole 
process  of  formation  of  this  volcanic  cone  was  observed 
and  recorded  by  residents  of  the  region.  Other  similar 
eruptions  have  been  observed,  but  perhaps  this  is  the  best 
known.  We  have  here  what  may  well  be  called  a  young 
volcano.  .  The  cone  to-day  is  almost  perfect  in  form. 


CINDER  CONE  NEAR  MOUNT  LASSEN. 

In  northern  California,  near  Mt.  Lassen,  which  has  itself 
recently  become  active,  another  almost  perfect  cone  of  this 
kind  is  found,  which  was  probably  formed  much  more  re- 
cently than  Monte  Nuovo.  From  this  cone  both  cinders 
and  liquid  material  or  lava  were  ejected. 


VESUVIUS 


443 


211.  Vesuvius.  —  When  the  Roman  nobles  were  building 
their  magnificent  villas  and  baths  along  the  shore  of  the 
Bay  of  Naples,  the  scenic  beauty  of  the  region  was  greatly 
increased  by  a  mountain  in  the  shape  of  a  truncated  cone, 
which  rose  from  the  plain  a  few  miles  back  from  the 
shore.  Its  sides,  nearly  to  the  summit,  were  covered 
with  beautiful  fields. 

In  the  top  of  the  mountain  was  a  deep  depression  some 
three  miles  in  diameter,  partly  filled  with  water  and  almost 


VESUVIUS  AND  NAPLES. 

entirely  surrounded  by  precipitous  rock  cliffs.  There 
were  no  signs  of  internal  disturbance.  Around  the  moun- 
tain were  scattered  prosperous  cities,  the  soil  was  fertile, 
the  vegetation  luxuriant.  To  this  natural  fortress  Spar- 
tacus,  the  gladiator,  retreated  when  he  first  began  to  defy 
the  power  of  Rome. 


444 


FIRST   YEAR   SCIENCE 


In  63  A.D.  the  region  'about  the  mountain  was  shaken 
by  a  severe  earthquake  which  did  much  damage.  This 
was  followed  by  other  earthquakes  during  a  period  of  six- 
teen years.  In  August,  79,  the  whole  region  was  fright- 
fully shaken,  and  the  previously  quiet  mountain  began  to 
belch  forth  volcanic  dust,  cinders  and  stones,  so  that  for 
miles  around  the  sun  was  obscured,  and  a  pall  of  utter 
darkness  shrouded  the  country,  lighted  at  intervals  by 
terrific  flashes  of  lightning. 

A  large  part  of  the  ancient  crater,  now  known  as  Monte 
Somma,  was  blown  away,  and  the  villas  and  towns  near 
the  mountain  were  covered  with  the  ash  and  cinders 
ejected.  So  deep  were  many  of  these  buried  that  their 
sites  were  utterly  forgotten.  Pompeii  and  Herculaneum, 
after  lying  buried  and  almost  forgotten  for  hundreds  of 
years,  have  been  recently  partially  uncovered. 

These  fossil  cities  show  the  people  of  to-day  how  the 
ancient  Romans  lived  and  built.  The  topography  of 

the  country  and  the 
coast  line  were  greatly 
changed  by  this  erup- 
tion. Pompeii  formerly 
was  a  sea  coast  city  at 
the  mouth  of  a  river. 
It  is  now  a  mile  or  more 
from  the  sea  and  at  a 
considerable  distance 
from  the  river. 

From  the  date  of  its 
first  historic  eruption 
until  the  present  time  Vesuvius  has  had  active  periods 
and  periods  when  quiet  or  dormant.  Sometimes  the 
activity  is  mild,  and  at  other  times  tremendously  violent. 
At  times  the  material  ejected  is  fragmental  and  at  other 


MOUNT  VESUVIUS. 
Showing  the  famous  eruption  of  1872. 


MOUNT  PELEE 


445 


times  streams  of  molten  lava  pour  down  its  sides.  Its 
ever  changing  cone,  unlike  that  of  Monte  Nuovo,  is  com- 
posed partly  of  ash  and  partly  of  consolidated  lavas.  Even 
as  late  as  1907  a  tremendous  outpouring  of  ash  took  place 
which  devastated  a  considerable  area. 


MOUNT  PELEE  AND  THE  RUINS  OF  ST.  PIERRE. 

212.   Mount  Pelee.  —  At  the   north  end  of  the  island  of 
Martinique    in    the  West    Indies   rose    a   conical-shaped 


446  FIRST  YEAR   SCIENCE 

1  •& 

mountain.  In  a  hollow  bowl-like  depression  at  the  top 
lay  a  beautiful  little  lake  some  450  feet  in  circumference. 
The  mountain  and  lake  were  pleasure  resorts  for  the  peo- 
ple of  the  city  of  St.  Pierre.  According  to  legend  this 
mountain  had  been  violently  eruptive,  but  in  historic  time 
there  had  been  no  indication  of  this  except  one  night  in 
1851  when  the  volcano  had  grumbled  and  a  slight  fall  of 
volcanic  ash  was  found  in  the  morning  over  some  of  the 
surrounding  region. 

On  April  25,  1902,  people  began  to  see  smoke  rising 
from  the  vicinity  of  the  mountain  and  from  this  time  on 
till  the  final  catastrophe  smoke  and  steam  came  out  in 
small  quantities.  By  May  6  the  volcano  was  in  full  erup- 
tion. On  the  morning  of  May  6  the  cable  operator  at 
St.  Pierre  cabled,  "  Red-hot  stones  are  falling  here,  don't 
know  how  long  I  can  hold  out."  This  was  the  last  dispatch 
sent  over  the  cable. 

About  8  o'clock  on  the  morning  of  the  8th  a  great  cloud 
of  incandescent  ash  and  steam  erupted,  swept  rapidly  down 
the  mountain  toward  St.  Pierre  and  in  less  than  three 
minutes  killed  30,000  people,  set  the  city  on  fire  and  de- 
stroyed 17  ships  at  anchor  in  the  harbor.  Thus  within 
two  weeks  from  the  time  of  the  first  warning  a  rich  and 
densely  populated  region  was  made  a  desolate,  lifeless,  fire- 
swept  desert. 

213.  The  Azores.  —  About  800  miles  west  of  Portugal 
rises  from  the  depths  of  the  Atlantic  a  group  of  nine  islands, 
the  Azores.  They  have  an  area  of  about  1000  square  miles, 
and  the  soil  is  very  fertile.  The  islands  are  mountainous, 
one  of  the  mountains  rising  to  between  7000  and  8000 
feet  above  the  sea.  Like  other  lofty  islands  of  the  deep 
ocean  these  are  volcanic.  Although  at  present  not  actively 
eruptive  they  abound  in  hot  springs  and  have  frequent 
earthquakes. 


VOLCANOES   OF  THE   UNITED   STATES 


447 


Volcanic  cones  are  abundantly  scattered  over  the  islands, 
and  comparatively  fresh  lava  flows  are  not  wanting.  In 
recent  times  small  islands  have  arisen  in  the  group  and 
eruptions  have  taken  place.  There  are  no  other  islands 


SAN  MIGUEL  HARBOR  IN  THE  AZORES. 
Notice  the  volcanic  cones  in  the  distance. 

near  them.  Their  formation  is  due  entirely  to  volcanic 
forces.  Islands  of  this  kind  and  coral  islands  are  the  only 
projections  rising  to  the  surface  from  the  deep  ocean  floor. 
214.  Volcanoes  of  the  United  States.  —  In  the  Cordilleran 
region  of  the  United  States,  west  of  the  meridian  of 
Denver,  there  are  a  score  or  more  of  lofty  peaks  which 
show  conclusive  evidence  of  volcanic  origin.  Until  the 
summer  of  1914  when  Mt.  Lassen  suddenly  began  to  erupt, 
none  of  these  had  been  active  since  white  men  became 
familiar  with  the  region.  Some  of  the  cones  have  been  so 
recently  formed  that  the  forces  of  erosion  have  not  had 


448 


..FIRST   YEAR   SCIENCE 


time   to  wear  them  away  extensively, 
almost  perfect  in  shape  like  Mt.  Shasta. 


Thus   they   are 
Others,  like  Mt. 


MOUNT  LASSEN  IN  ERUPTION. 

This  volcano,  after  being  dormant  for  centuries,  suddenly  renewed 
its  activity  in  1914. 

Hood,  have  been  deeply  eroded,  but  not  sufficiently  to  ob- 
literate the  conical  outline. 

In  the  region  around  Mt.  Taylor  erosion  has  progressed 
so  far  that  only  the  roots  of  the  volcanoes  still  remain,  the 
cones  having  been  entirely  worn  away  and  only  the  central 
plug  of  lava  left,  forming  what  is  called  a  volcanic  neck. 
In  the  Aleutian  Islands  are  numerous  volcanoes  which  are 


VOLCANOES   OF  THE   UNITED  STATES 


449 


still  active,  and  in  Hawaii  are  some  of  the  greatest  volcanoes 
on  the  earth. 


MOUNT  HOOD. 
A  beautiful  old  volcanic  cone. 


In  Crater  Lake  we  have  a  volcano  whose  normal  develop- 
ment  has  been  interrupted    by  an  accident,  its   summit 


VOLCANIC  NECKS  NEAR  MOUNT  TAYLOR. 

having  fallen  in,  leaving  a  circular  depression  in  the  top  of 
the  mountain  surrounded  by  steep  walls  and  now  nearly 


450 


FIRST   TEAR   SCIENCE 


CKATER  LAKE. 


filled  with  water.     Except  for  the  water  filling,  this  de- 
capitated volcano  or  caldera  quite  closely  resembles    the 


LAVA  FLOW  IN  THE  HAWAIIAN  ISLANDS. 
Liquid  lava  flowing  over  a  cliff. 


LIFE  HISTORY  OF  A    VOLCANO  451 

probable    condition  of  Vesuvius  before  the  eruption  of 

79  A.D. 


A  HAWAIIAN  CRATER. 

215.  Life  History  of  a  Volcano.  —  A  volcano  is  simply  a 
place  in  the  earth's  surface  where  molten  rock  or  f rag- 
mental  material  from  within  the  earth  is  extruded.  If 
the  extrusion  of  the  lava  is  accompanied  by  gaseous  ex- 
plosions, it  will  be  blown  into  fragments  which  will  fall 
around  the  vent  and  build  up  a  steep-sided  cone,  like  that 
of  Monte  Nuovo.  If  the  eruption  is  less  violent,  lava  may 
flow  from  the  crater  or  pour  from  openings  formed  in  its  sides. 

As  the  same  volcano  usually  ejects  both  the  f  ragmen  tal 
and  molten  material,  volcanic  cones  are  generally  complex 
in  their  composition.  Sometimes,  however,  cones  are 
found  which  are  composed  entirely  of  one  sort  of  material. 
Those  which  are  largely  or  entirely  formed  of  lava  have 
a  much  gentler  slope  than  the  others.  Such  are  the  gre^t 
Hawaiian  cones. 


452  FIRST  YEAR  SCIENCE 

Some  volcanoes,  like  Stromboli,  are  in  constant  eruption; 
others,  like  Etna,  vary  their  eruptions  with  irregular 
periods  of  rest,  while  still  others  remain  quiet  for  very 
long  periods  and  then  suddenly  break  forth  with  terrific 
force,  as  did  Vesuvius  in  79.  As  a  rule,  but  not  always, 


CROSS  SECTION  OF  A  LAVA  FLOW. 

eruptions  are  preceded  and  accompanied  by  earthquakes. 
Just  why  volcanoes  erupt  is  unknown. 

After  a  volcanic  cone  has  come  into  being  it  is  subject 
to  the  action  of  the  erosive  forces,  and  unless  its  material 
is  renewed  by  fresh  outpourings  it  will  in  time  be  worn 
down.  Unlike  other  kinds  of  mountains  it  is  also  liable 
to  disruption  by  explosions  from  within. 

216.  Distribution  of  Volcanoes.  —  The  number  of  active 
volcanoes  on  the  earth  is  about  300.  Most  of  them  are 
situated  on  the  borders  of  the  continents,  on  islands  near 
the  continents,  or  else  they  form  islands  in  the  deep  sea. 
Soundings  show  that  there  are  many  peaks  in  the  sea 


SUMMARY 


453 


which  have  not  reached  the  surface;  these  are  probably 
volcanic.  Few  volcanoes  are  far  from  the  sea  although 
there  is  an  active  crater  in  Africa  several  hundred  miles 
from  the  Indian  Ocean. 

Extinct  cones  are  sometimes  found  far  in  the  interior  of 
continents,  as  the  Spanish  Peaks  of  Colorado,  which  are 
more  than  800  miles  from  the  present  coast.  Many  of 
the  once  active  deep-sea  cones  have  now  become  extinct, 
and  their  gently  sloping  shores  have  been  cut  back  into 


THE  CITY  OF  ST.  HELENA. 

cliffs  which  rise  abruptly  from  the  sea.  One  of  these,  St. 
Helena,  rising  from  the  depths  of  the  Atlantic  Ocean  and 
bounded  by  precipitous  cliffsj  is  noted  as  being  the  place 
of  exile  of  the  Emperor  Napoleon  I  of  France. 

Summary.  —  Volcanoes  are  openings  in  the  earth's 
crust  through  which  portions  of  melted  earth  material 
pour  forth.  This  material  may  be  ash  and  cinders  or  it 
may  be  molten  lava. 


454  .FIRST   YEAR   SCIENCE 

Some  of  the  most  interesting  or  best-known  volcanoes 
are  in  Italy.  Monte  Nuovo,  the  New  Mountain  near 
Naples,  is  so  called  because  it  came  iri-to  being  in  a  few 
days.  Vesuvius,  which  dominates  all  views  of  Naples,  is 
perhaps  the  world's  most  famous  volcano.  Mount  Pelee 
in  Martinique  had  perhaps  the  most  disastrous  and  spec- 
tacular eruption  in  all  history.  The  Azores  islands  are 
all  volcanic  in  their  formation,  and  Hawaii  has  some  of 
the  world's  greatest  volcanoes. 

The  United  States  has  a  number  of  volcanic  peaks,  like 
Mt.  Shasta  and  Mt.  Hood,  but  until  the  recent  eruption 
of  Mt.  Lassen,  it  had  no  active  volcano. 

QUESTIONS 

What  is  the  condition  of  the  earth's  interior  ? 

Describe  the  eruption  and  present  condition  of  Monte  Nuovo. 

What  has  been  the  history  of  Vesuvius? 

What  is  Mount  Pelee's  story  ? 

How  were  the  Azores  formed  ? 

What  volcanoes  are  there  in  the  United  States? 

Give  the  life  history  of  a  volcano. 

Where  are  volcanoes  found  ? 


APPENDIX 


217.  Determination  of  Latitude.  —  In  Fig.  121  consider 
the  sun  as  vertically  above  the  point  where  our  meridian 
crosses  the  equator  and  the  lines  AB  and  ED  as  repre- 
senting rays  from  the  sun.  The  line  FI  tangent  at  the 
point  A  will  represent  a  level  surface  at  that  point.  Draw 
the  line  OH  through  the  point  A.  It  will  be  at  right 
angles  to  the  tangent  line  FL  The  latitude  of  the  point 
A  is  measured  by  the 
angle  EGA,  as  this  angle 
measures  the  number  of 
degrees  of  latitude  be- 
tween the  point  E, 
which  is  on  the  equator, 


and  the  point  A. 

It  can  be  proved  by 
geometry  that  the  angle 
HAB  is  equal  to  the 
angle  HCE,  since  if  the  Fig.  121. 

sun  is  vertical,  the  line 

OED  is  a  straight  line.  The  angle  HAB  is  equal  to 
a  right  angle,  or  90°  minus  the  angle  BAI.  As  the 
angle  BAI  can  be  easily  found  by  measuring  the  elevation 
of  the  sun  'above  a  horizontal  plane,  it  is  not  a  difficult 
thing  to  find  the  latitude  of  a  place  when  the  sun  is  ver- 
tical at  the  equator. 

As  the  sun  is  vertical  at  the  equator  but  twice  in  a  year, 
on  March  21  and  September  23,  this  method  can  be  used 

455 


456  APPENDIX 

without  modification  only  on  those  days ;  but  since  the 
angle  of  the  sun  above  or  below  the  plane  of  the  equator  is 
given  in  the  Nautical  Almanac  for  every  day  in  the  year, 
by  adding  this  angle  to  the  angle  BA I  when  the  sun  is 
above  the  equator,  and  subtracting  it  when  the  sun  is  be- 
low the  equator,  the  latitude  of  a  place  can  be  found  for 
any  day. 

On  board  ship,  every  fair  day,  the  officers  will  be  seen 
just  before  noon  coming  on  deck  with  their  sextants  to 
take  the  elevation  of  the  sun.  They  find  the  elevation 
several  times  until  they  are  sure  that  the  sun  has  reached 
its  highest  point,  and  at  this  moment  they  call  for  the 
time  to  be  taken  on  the  chronometer;  for  when  the  sun 
reaches  its  highest  point,  it  is  noon  for  that  place.  Thus 
by  making  use  of  this  one  observation  they  are  enabled, 
with  the  help  of  the  chronometer,  to  find  both  their  latitude 
and  their  longitude,  or  their  exact  position  on  the  earth. 

218.  Topographical  Maps.  —  Maps  which  attempt  to  show 
the  surface  features  of  the  earth  are  called  topographical 
maps.  There  are  several  ways  in  which  we  may  try  to 
show  on  a  map  the  irregularities  of  the  surface.  One  of 
these  is  shading,  that  is,  making  the  hills  and  ridges  light, 
while  the  valleys  are  shaded  dark.  A  somewhat  similar 
way  is  to  draw  short  broken  lines  in  the  direction  of  the 
slopes.  This  gives  a  more  accurate  representation  of  the 
steepness  of  the  descents,  since  the  lines  are  made  short 
and  heavy  when  the  slope  is  steep  and  longer  and  lighter 
when  it  is  gradual.  Such  maps  are  called  hachure  maps. 

The  commonest  way  in  this  country  is  to  draw  lines 
connecting  places  of  equal  elevation.  These  lines  wander 
in  and  out  of  the  valleys  and  around  the  hills,  but  always 
pass  through  places  which  are  of  the  same  altitude.  The 
distances  apart  of  the  lines  vary  continually,  but  the  eleva- 
tions never.  From  these  maps  the  height  of  any  place  can 


PROJECTIONS  457 

be  determined  with  great  accuracy,  for  its  height  will  be 
indicated  by  the  line  passing  through  it  or  near  it.  These 
maps  are  called  contour  maps. 

219.  Contour  Maps.  —  Although  it  is  easy  to  find  the  ele- 
vations of  places  on  a  contour  map,  it  is  hard  to  get  a 
clear  idea  of  what  a  contour  map  really  expresses.     The 
best  way  to  gain  an  appreciation  of  a  contour  map  is  to 
get  a  map  of  the  region  in  which  you  live,  take  it  into  the 
field,  and  study  map  and  region  together.     Another  ex- 
cellent way  is  to  make  a  contour  map  of  a  model.     When 
once  you  have  made  a  map  of  this  kind,  you  will  readily 
understand  all  other  similar  maps. 

We  must  remember  that  a  contour  is  the  projection  on 
a  flat  surface  of  a  line  which  passes  through  places  of 
equal  elevation.  It  shows  where  the  margin  of  water 
would  come  if  the  place  in  question  were  submerged  to  a 
given  depth.  No  two  contours  can  possibly  cross  each 
other,  as  no  place  can  have  two  elevations.  No  contours 
can  ever  end  except  at  the  edge  of  the  map,  for  a  sheet  of 
water  must  have  a  continuous  boundary  and  only  where 
the  map  terminates  can  the  line  representing  the  edge  of 
the  water  appear  to  end. 

Experiment  133.  —  Provide  each  pupil  with  a  contour  map  represent- 
ing the  home  locality  if  possible ;  if  not,  use  the  contour  map  facing 
page  345.  Let  the  teacher  or  different  pupils  pick  out  places  and  ask 
some  one  to  give  their  elevations.  In  this  way  you  will  get  an  idea 
of  how  elevations  can  be  determined  by  use  of  a  contour  map. 
Notice  the  different  topographical  symbols  used  on  the  map. 

220.  Maps  of  Curved  Surfaces.     Projections.  —  The   accu- 
rate mapping  of  small   areas   offers    no   great    difficulty 
because  these  are  practically  flat,  but  when  an  attempt  is 
made  to  represent  a  curved  surface  upon  a  flat  surface, 
difficulties  present  themselves  which  are  insurmountable. 
If  the  rind  of  an  orange  is  taken  off,  it  cannot  be  made  to 


458  APPENDIX 

lie  flat,  and  if  crushed  into  this  shape,  it  will  break  into 
pieces  and  only  partly  cover  the  surface  over  which  it 
spreads.  The  same  is  true  of  any  curved  surface.  Thus 
the  continents  of  the  earth,  if  they  were  flattened  out, 
would  of  necessity  be  broken  into  fragments.  If  they 
could  not  themselves  be  made  to  occupy  a  flat  surface, 
then  no  accurate  map  of  them  can  be  made  on  such  a  sur- 
face. 

Although  there  are  several  ways  of  representing  a 
curved  surface  upon  a  flat  surface,  yet  no  method  has  been 
found  which  is  perfectly  satisfactory.  If  the  areas  are  in 
the  right  proportions,  the  outlines  are  not;  and  when  the 
outlines  are  right,  the  areas  are  not.  These  different  ways 
of  mapping  the  surface  of  the  earth  are  called  projections. 
As  a  large  part  of  our  knowledge  of  the  earth's  surface  is 
obtained  from  maps,  it  is  very  essential  to  have  some  idea 
of  how  these  maps  are  made  and  wherein  the  essential 
error  of  each  consists.  The  two  important  kinds  of  pro- 
jection are  the  cylindrical  and  the  stereographic. 

221.  Cylindrical  Projection.  —  In  this  projection  it  is  con- 
sidered that  a  cylinder  is  w  rapped  around  the  globe  touch- 
ing at  the  equator.  The  points  on  the  globe  are  projected 
on  to  the  cylinder  by  lines  drawn  from  the  center  of  the 
globe  through  each  point  to  the  surface  of  the  cylinder. 
Thus  the  meridians  become  straight  lines  always  the  same 
distance  apart ;  and  the  parallels  of  latitude  are  also 
straight  lines,  but  their  distances  apart  will  increase  with 
the  latitude.  The  poles  themselves,  being  in  the  diameter 
of  the  cylinder,  lie  at  an  infinite  distance  from  the  equator. 

When  such  a  cylinder  is  unrolled  it  forms  a  skeleton 
map  on  which  can  be  plotted  places  whose  latitude  and 
longitude  are  known.  The  directions  north  and  south  will 
be  up  and  down  the  map,  and  east  and  west  to  the  right 
and  left.  This  cylindrical  projection  causes  a  degree  of 


STEEEOGEAPHIC  PROJECTION  459 

latitude  to  vary  from  about  ^J^  of  the  earth's  circumference 
at  the  equator  to  infinity  at  the  poles  ;  and  a  degree  of 
longitude,  which  near  the  poles  has  almost  no  length,  is 
made  to  have  a  length  everywhere  equal  to  that  of  a 
degree  on  the  equator.  Thus  passing  from  the  equator 
toward  the  poles,  the  areas  of  surfaces  on  the  earth  are 
increased  when  represented  on  this  projection,  but  the 
increase  east  and  west  and  the  increase  north  and  south 
are  riot  equal.  This  causes  the  shape  of  the  portions  of 
the  earth  farthest  from  the  equator  to  be  much  distorted. 

The  Mercator  projection  is  the  most  commonly  used  of 
all  projections.  It  is  a  simple  modification  of  the  cylin- 
drical, in  which  the  exaggeration  north  and  south  is  made 
equal  to  that  east  and  west.  In  this  projection  the  polar 
regions  are  greatly  enlarged.  This  explains  why  Green- 
land, which  on  the  globe  is  of  comparatively  small  size, 
when  seen  on  the  ordinary  map  of  the  world  is  half  the 
size  of  North  America.  The  great  advantage  of  this  pro- 
jection is  that  the  meridians  and  parallels  are  both  repre- 
sented by  straight  lines.  A  navigator  can  thus  at  any 
time  find  his  course  by  drawing  a  straight  line  joining  the 
places  between  which  he  is  sailing.  This  is  why  most 
nautical  charts  are  constructed  on  this  projection.  But 
to  geographers  this  projection  is  not  of  as  great  value  as 
some  others  since  the  shapes  of  the  land  masses  are  so 
much  distorted. 

222.  Stereographic  Projection.  —  Of  the  hemispherical  pro- 
jections probably  the  best  for  study  is  the  stereographic. 
This,  or  a  slight  modification  of  it,  is  the  projection  upon 
which  are  constructed  the  hemispherical  maps  usually  seen. 
In  it  a  plane  is  considered  as  held  tangent  at  a  certain 
point  on  the  globe  and  from  a  point  on  the  globe  directly 
opposite  the  point  of  tangency,  lines  are  drawn  to  the 
plane  through  the  intersections  of  the  parallels  of  latitude 


460  APPENDIX 

'  '  ./* 

and  longitude.     Through  these  projected  intersections  the 

meridians  and  parallels  of  latitude  are  drawn. 

In  this  projection,  places  near  the  k  point  of  tangency 
have  their  outlines  correctly  reproduced,  but  the  farther 
away  a  place  is  from  this  point,  the  greater  the  distortion. 
This  distortion,  however,  is  never  as  great  as  that  at  the 
north  and  south  in  the  cylindrical  or  Mercator  projections. 
In  the  stereo-graphic  projection,  however,  the  directions 
north  and  south  and  east  .and  west  must  be  traced  on  a 
curved  line,  thus  making  it  much  more  difficult  to  tell  at 
a  glance  the  direction  of  one  place  from  another.  It  is 
not  possible  on  this  projection  to  show  more  than  one 
half  the  earth's  surface  on  a  single  map. 


INDEX 


References  are  to  pages. 


Abdo'men 234 

Adiaba'tic  heating-     ....  123 

Agriculture,  dry  farming    .     .  101 

fertilizing 106 

irrigation 102 

of  coastal  plains 39 

See  also  Agricultural  Soils. 
Air,  see  Atmosphere. 

Alcohol,  effects  of 237 

Alimentary  canal 233 

Al'kali  soils 103 

effect  of,  upon  plants  ....  184 
See  Soils. 

Allu'vial  cones  (fans)      ...  349 

AnemSm'eter 144 

Angle  of  incidence  and  of  re- 
flection        63 

Animals 217 

circulation      . 227 

classification 217 

inver'tebrates 218-224 

insects 221 

protozo'a. 218 

worms 220 

ver'tebrates 225 

distribution 254 

effects  of  glacial  age  upon   .     .  384 

food 233 

of  mountain  regions    ....  432 

respiration 225 

Anther 201 

Antitox'in 216 

Aqueous  humor 231 

Arctu'rus 5 

Arteries 228 

picture 229 

Arte'sian  wells 318 

of  coastal  plains 398 

picture 315 

Ash,  volcanic    ....   442,  444,  453 

As'teroids,  see  Planetoids. 

Atmosphere,  barometers     .     .  119 

barometric  gradient    ....  142 

capacity  for  moisture  ....  124 


Atmosphere  —  Continued 
effect  of  water  bodies  on      .     .    137 

expansion 115 

forms  of  moisture,  clouds,  fog, 

etc 127 

heating 55,  123,  130-136 

height 122 

humidity,  absolute  and  relative    126 

hygrom'eter 127 

I'sobars 136,  140,  141 

isotherms 135,  136,  137 

monsoons 153 

natural  phenomena,  rainbow, 
mirage  (meerahzh'),  aurora  .    128 

origin Ill 

pressure 117,  137 

rainfall       154-160 

spectrum 127 

weather  maps 136 

weight 115 

wind  belts 148 

Atolls'      . 289, 307 

picture 286 

Attraction,  see  Gravitation. 

Auditory  nerve 232 

Auricle 229 

Aurora*bo-re-al'is 129 

Avalanches 431 

Axis  of  the  earth 3 

Azores',  volcanoes  of    ....    446 

Bacte'ria 209-218 

picture 213 

''Bad  Lands"      ......    328 

picture 327 

Barograph 122 

Barometers,     mercurial      and 

aneroid 119-122 

Barometric  gradient      .     .     .    142 

Bays 399 

Beaches 68-70 

formation 296 

See   also    Coastal  Plains  and 
Coasts. 


FIRST   YEAR   SCIENCE 


References  are  to  pages. 


Bee,  see  Honey-bee. 
Biplane,  picture  of 

Bison 

picture  .... 
BItu'minous  coal 
Blizzard  . 


...  9 
...  432 
...  406 
...  78 
...  171 

Blood,  corpuscles 228 

circulation 227 

Bottom  lands 402 

Bowlders 367 

erratic    . 379 

pictures 369,  380 

Brain 224 

picture 225 

Breadmaking 211 

Budding  . 192 

Buds,  terminal  and  axillary  .     .     192 

Buffalo 406,432 

Buttes  (biuts)       ....      412, 413 


Cactus      .        .     . 
Calde'ra  .... 

Calorie  of  heat   . 
Calyx.     .  ..     .     . 

Cambium  layer  . 

Camera  obscura 

eye  compared  to 


,  .  245 
.  .  450 
.  .  57 
.  .  201 

189,  191 
,  .  58 

230,  231 


Capillaries 226 

Capillarity 97,  187 

Car' bony 'drates     .     .   197,  235,  236 
Carbon  dioxide,  in  air   112,  114,  178 

in  animals 217 

in  plants 196,  208 

in  yeast 7    .    211 

Cattle  tick 220 

Cells,  electric 165 

of  plants 186 

Centigrade  thermometer      .      51 

Centrifugal  force 9,  11 

Chlo'rophyll 197,  209 

Cinders,  volcanic      .     .   442,  444,  453 
Circulation  of  the  blood    .     .    228 

picture .    229 

Clay,  see  Soils. 

Climate 174-178 

effects  upon  plants  and  animals    176 
upon  distribution  of  life   .     .    256 
upon  man     .......     177 

Clouds 126 

See  also  Moisture. 


Coal •   .     .     .      78 

Coastal  plains,  see  Plains. 

Coasts     .     .  " 292 

beaches 296 

depressed  and  elevated      .    301,  304 

harbors 307 

of  the  U.  S 309 

safeguarding  the 307 

sand  bars 297,  302 

spits  .     .     .     .     .  » .     .     .     .     .    297 

waves 294 

Columbus,  Christopher 
(1445  ?-1506) ,  discoverer  of 
the  declination  of  the  mag- 
netic needle 34 

Compass,  Mariners'      ...     40,  41 

points  of  the 23 

Conduction  of  heat  ....  53 
Conductors,  of  electricity  .  .  161 

of  heat 53 

Conservation  of  energy  .  46-49 
Continental  shelf  .  .  .  272,  273 
Convection  of  heat  ....  54 

Cooking 238 

Coral  islands  or  reefs   288,  289, 293 

atolls 289 

Corol'la 201 

Coro'na 128 

Cor'puscles,  red  and  white  .  .  228 
Crevas'ses  of  glaciers  .  .  .  365 

Cri'noid,  picture  of 276 

Currents  of  the  sea  ....    281 

map 280 

Cyclones     . 168 

map 172 

Darwin,  Charles  (1809-1882)    .      19 

Day,  lunar 29 

mean  solar 31,  32 

sidereal       .     .     .• 29 

solar 29 

Day  and  night,  cause  ....      21 
of  equal  length 28 

Dead  Sea 325 

picture 324 

Declination  of  the  magnetic 

needle 34,  35 

Degree  of  latitude  and  longi- 
tude   32 

Delta 299,  307,  350-352 


INDEX 


References  are  to  pages. 


Delta,— Continued 

of  the  Mississippi,  pictures 
Desert,  adaptability  to     . 

irrigation 

life 


pictures      

reflectors  used  in     .     . 

sandstorms      .... 

Dew 

Diameter  of  the  earth 
Diaphragm      .... 

Di'atoms 

Di'cotyle'dons    .     .     . 

Directions 

Disinfectants .... 

Divides 

Dol'drums 

Draft  (of  a  stove)      .     . 
Drainage,  basins  of  U.  S. 

effected  by  glaciers 

of  level  areas .... 

See  also  Rivers. 
Drum'lins    .     .     .     .    . 

picture   

Dry  farming   .... 
Dunes,  sand 


352,356 

.  245 

.  102 

.  258 

.  258 

258,  259 

.  63 

.  258 

.  126 

.  16 

.  227 

.  249 

1! »0,  207 

.  23 

.  215 

.  328 

.  149 

.  116 

.  354' 

.  380 

.  391 


.     .    376 
.     .    375 

.     .     101 
302,  387 


Ear,  parts  of 231 

picture 231 

Earth,  ancient  ideas  of  ...  3,  22 

as  planet 3-6 

axis  and  poles 3 

inclination  of  axis  ....  25-28 

interior 21 

land  and  water .68-70 

land  surfaces 70 

magnetic  fields 34-43 

man  and 19,  20 

"  oblate  spheroid  "  ....  16 
revolution  around  the  sun  .  23-30 

rotation 22 

satellite 11 

shape  and  diameter  ....  16 

size 18 

surface 16,  68 

water 71 

Earthquakes 425-428 

Electric  doorbell   .  165 


Electricity, 

cells  ..........  165 

conductors      .......  161 

lightning    ........  162 

telegraph    ......  165-167 

thunder-storms    ......  163 

two  kinds  ........  161 

Electro-magnets    .....  39 

use  in  telegraphy    .....  165 

Ellipse'     .........  24 

Energy,  conservation  of   .     .     46,  47 

from  food   ........  236 

in  animals  ........  217 

in  plants     .....    198,  208,  209 

of  the  sun  ......     15,  45-67 

potential  and  kinetic  ...     45,  46 

Epiglot'tis  ........  226 

Equator  .........  25 

heat  equator  .......  148 

Equinox,  autumnal  and  vernal  28 

Erosion,  by  water     .....  326 

of  Colorado  River   .....  410 

of  Mt.  Taylor  volcano      ...  448 

of  rivers     ........  333 

of  winds     ........  386 

on  "  Great  Plains  "     ....  404 

Esker  ..........  377 

picture   .........  376 

Estuaries    .     .     ......  305 

Evaporation  from  the  sea     .  289 

Extension  of  matter      ...  7 

Eye,  like  camera  ......  58 

parts  of  .........  230 

picture  ....     .....  231 

Eyelid      .........  230 


Fahrenheit,     Gabriel 

1736) 

Fall  line 
Falls          ...... 


(1686- 

51 

397 

329-332,  398 


of  Niagara      .......  332 

ofYosemite    .......  330 

Fans    ..........  349 

picture   .........  348 

Fats  as  food    .......  235 

Faults      .........  415 

See  also  Mountains. 

Fauna      .........  247 

of  the  U.  S  ........  247 

Ferrel's  Law  ......  148 


•FIRST   Y_EAR   SCIENCE 


References  are  to  pages. 


Fiords 306 

pictures 305,  306 

Fishing  banks 273 

Flies,  carriers  of  disease    .     .    .    216 

Flood  plain 336 

See  also  Plains. 

Flora 247 

of  the  U.  S 266 

Flowers 200-205 

dispersal  of  seeds 205 

fertilization 202 

parts  of       201 

Foci  of  an  ellipse 24 

Fog- 126 

See  also  Humidity. 

Foods 233-240 

digestion 233 

necessary  —  protein,  fats,  carbo- 
hydrates             235-238 

preparation 238 

uses 233 

Force,  magnetic  fields  of  .    .     .      39 
Forces,  composition  and  resolu- 
tion of,  see  figure  5,  page  11. 

Forestry 262 

bad 262,263 

effects  of    ......      264,  269 

good 265,  266 

Fossils 242 

Franklin ,  Benjamin  ( 1 706-1790)  162 

Frigid  zones 25-28 

Fungi  (fun'ji) 209 

mushrooms  and  toadstools       .    211 

yeast 210 

Furnace,  hot  water  and  hot  air      54 
picture 55 


Gastric  juice  .... 
Geography,  old  ideas  of 
Germs 

See  also  Bacteria. 
Geysers 

pictures      

Glacial  flour  .... 
Glacial  period    .     .    . 

plants  and  animals  of 
Glacial  strise  (strl'ee) 

Glaciers       

Globigeri'na    .... 

picture  


.  234 

3,22 

92,  215 

319-321 
320-321 

.  368 
379-386 
384-386 

.  368 
363-386 
249,  276 

.    277 


Grafting 192 

Gravel,  see  feoils. 

Gravitation 10 

Gravity 7,  10 

Greenwich   (grgnich)   in  Eng- 
land           32-34 

Ground  moraine 368 

Gulf  Stream 282 

map 280 

HEemoglo'bin      ......  228 

Hail 157 

Halos 128 

Harbors       307-311 

Heart        229 

picture 230 

Heat 47-49,130-137 

and  atmosphere 130 

comparative    heat    lines    (iso- 
therms)       ....    135,  136,  137 

measurement 49 

specific 57 

transference, 

conduction 53 

convection 54 

radiation 55 

transformation  of,  picture   .     .  46 

variation  in 131 

"  Heat  lightning  "       ....  164 

Hercula'neum 444 

Hills 415 

Himalaya  Mts 19 

Hogans 414 

Honey-bee       222 

Horse  latitudes 152 

Humboldt  Current    ....  283 

map 280 

Humidity,  absolute    and    rela- 
tive       126 

See  also  Moisture  and  Atmos- 
phere. 
Hu'mus 91,  93,  94 

See  also  Soils. 

Hydrom'eter 72 

Hygrom'eter .  127 

Ice 51,73 

Icebergs 372-375 

in  glacial  lakes 380 

picture 381 


INDEX 


References  are  to  pages. 


Igneous  rocks 77 

See  also  Rocks. 
Incompressibility  of  air     .    .      73 

Inertia 8,  9,  10,  14 

Inlet 303 

Insolation  (sun  radiation)    .     .    130 
Intensity  of  light 61 

See  Light. 
International  Date  Line     .     .      30 

map 30 

Intestines 234 

picture 233 

Inver'tebrates    ....       218-224 

insects 221 

protozoa 218 

worms 220 

I'ris  of  the  eye 230 

sketch  of 231 

Irrigation 102 

in  squares  and  furrows    .      102,  103 
Islands,  atolls      ....      289, 307 

coral       289 

_  life  on 260 

I'sobars .    138 

_  maps  of       ......      140,  141 

I'sogonic  lines 35,  36 

I'sotherms 135 

maps  of       ......      136,  137 

Japan  Current 282 

map 280 

Jelly  fish 249 

Joule,  James  P.  (1818-1889)     .  48 

Jupiter,  the  planet 4,  5 

Kangaroo 255 

Kinet'ic  energy 45 

in  plants 209 

See  also  Energy. 

Labrador  Current  ....  282 
map 280 

Lagoons' 289,  302 

Lakes  • 322-325 

Ag'assiz 381-382 

glacial 380 

salt 325 

Land  of  the  globe  ....  68 
changing  beaches  .  .  .  .  (58, 69 
characteristics 70,  71 


Land  of  the  globe—  Continued 

life 251,254 

rock  structure 79, 81 

soil 85-105 

subsoil 87 

weathering 82-84 

La/tent  energy,  see  Potential 
Energy. 

Lateral  moraine 367 

Latitude      ....       25,26,32,33 

determination  of  (appendix)     .    455 

La'va   ...      441,  442,  445,  447,  451 

pictures 450,  452 

Leaves  of  plants     .     .     .       193-200 

Levees' 339 

Life,  adaptability  of       ....    245 
affected  by  geographical  isola- 
tion  256,260 

by  climate 256 

by  man 261 

by  the  desert   ......    258 

distribution 243 

of  islands 260 

of  mountains 433 

of  the  land 251 

of  the  sea 248 

Light 47,57-66 

atmospheric  phenomena,  rain- 
bow, coronas,  halos      .     .     .    128 

aurora  borealis 129 

intensity 61 

mirage 129 

properties  of 58 

reflection 58,  59,  62-64 

refraction 60 

spectrum 127 

speed 64 

theory  of 65 

Lightning 162-164 

Lightning  rods  ......    163 

Lime,  limestone     ....    85-105 

See  Soils. 

Liver 234 

Loadstone 34-42 

See  Magnetism. 

Loam 88 

See  Soils. 

Loess  beds  (lo'es) 386 

Longitude 33,  34 

Lungs 226 


FIRST   YEAR   SCIENCE 


References  are  to  pages.- 


Magnetism 34 

declination  of  needle  ....  35 

"dip" 39 

effect  of  upon  compass    ...  40 

electro-magnets 38 

field  of  force 39 

magnets 37 

poles .-    .    .     .  35 

theory  of 42 

Mammoth  Cave 319 

Man, 

affected  by  the  Glacial  Age      .  385 

by  mountains 433 

and  soil 105 

Mangrove 293 

Maps: 

(a)  classes 

contour 457 

curved  projections      .     .  457 

cylindrical 458 

stereographic     ....  459 

topographical     ....  456 

weather 136 

(b)  charts 

cyclones  and  anticyclones  172 

date  line    ......  30 

drainage  of  U.  S.    .     .     .  354 

glacial  areas 383 

heat  belts 135 

isobars 140,  141 

isotherms  ....      136,  137 
land  and  water  hemispheres  68 

magnetic  declination      .  35 

magnetic  pole  regions     .  36 

meridians  and  parallels  .  32 

monsoons 153 

oceanic  currents     ...  280 

rainfall 155 

rainfail  of  U.  S.      ...  158 

storm  tracks 173 

time  belts 31 

wind  belts   .  .  149,  150,  151 

zones 25 

(c)  detail  maps 

Appalachian  Plateau .     .  416 

Chesapeake  Bay     .     .     .  399 

Coast  near  Atlantic  City  394 

Juniata  River,  facing  page  345 

Mississippi  mouths       338,  352 

Nahant 297 


Maps:  (c)  Continued 

Platte^River 335 

Mariners'  compass     .     .     .     40-41 
See  Magnetism. 

Mars 3,5 

picture 4 

Marsu'pials 254,  255 

Matter,  extension 7 

gravitation 10 

inertia 7,  8 

properties  of 7 

three  states  of 51,52 

Meanders 337 

picture 338 

Medial  moraine 367 

picture 368 

Meridians 32,  33 

maps 25,  32 

of  standard  time 31 

the  "  prime  " 32 

Mesa 412, 413 

Metamorphic  rocks   ....      79 
See  Rocks. 

Mirag-e 12!) 

Moisture 126 

clouds,  fog,  dew 127 

hygrometer 127 

point  of  saturation 126 

Molecules 49 

energy  of 45 

heated 6(5 

heat  transference  through   .     .      53 

magnetized 42 

Monadnocks 424 

Monocotyledons     .     .     .       190,  207 

Monsoons 153 

Monte  Nuovo 441 

Moon 11 

phases -  ...      14 

picture 12 

surface 13 

tides 284-287 

value  to  earth     ....    12,  13,  15 

Moraines,  ground     .....    368 

lateral,  terminal,  medial      .     .     367 

pictures 368,  369 

Morse,  Samuel  F.  B.  (1791-1872)  167 
Mosquito,  danger  from     .      218,  219 

Mount  Everest 17 

Mount  Lassen  .    442 


INDEX 


References  are  to  pages. 


Mount  Pelee        445 

Mountain  passes 329 

Mountains 415-438 

climatic  effects 429 

in  history 437 

kinds  of 

block 417 

folded 418 

low  (old) 422 

massive  (new) 420 

peaks 424 

peneplains 424 

peoples 433 

products 428 

ranges 425 

Mulches '.     .  101 

Mushrooms 211 

Natural  bridges      .     .     .     .     .    319 
pictures 317,  318 

Naval  Observatories  of  the 

U.  S .     .      29 

Neb'ula,  see  Nebular  Hypothesis. 

Neb'ular  Hypo'thesis    ...        6 

Nerves,  system  of 225 

of  sight,  hearing,  etc.       .     .  230-232 

Newton,  Sir  Isaac  (1642-1727) , 

first  law  of 8 

law  of  gravitation 10 

theory  of  light 65 

Niagara  Palls 331 

picture 332 

Nl'trogen,  effect  upon  plants    .     184 
in  air      ......   111,  114,  178 

in  soil 92,  212 

North  star        3,  23 

Northern  lights 129 


O'ases      

Oblate'  sphe'roid   . 
Ocean,  see  the  Sea. 
Oceanic  Islands 

Oil 

Ooze 

Opos'sum    .    .    .     . 
Optic  nerve     .     .     . 


.  .  258 

.  .  16 

.  .  260 

.  .  79 
'  .  .276 

.  .  255 

.  .  231 

Ore  in  mountains 428 

Osmo'sis 186 

O'vary  of  flower 201 

Oxbow  lakes  .                           .  338 


Oxygen  .    . 

as  plant  food 

for  animals  . 


.  73,  111,  114,  178 

183,  196,  197,  208, 

209,  239 

.  217,  226-228,  233 


Pan'creas 234 

Parallels  of  latitude  ...     32,  33 

Parasites 209 

picture  (mistletoe) 210 

Pe'neplain 424 

Petroleum 79 

Pistils 201 

Pith  rays     . 189 

Plains 391-407 

kinds  of 

belted 393 

coastal 392, 394-399 

embayed 399 

flood 336 

lake 400 

life  of 405-407 

river 401 

"the  Great" 403-405 

Planetary  winds 148 

Planetoids 6 

Planets,  distance  of      ....    5,  6 

movements 3 

names 4, 5 

Plants 182-212 

bacteria 212 

diseases 210 

effect  of  glacial  age  upon     .     .    384 

flowers 200 

fungi,  parasites,  etc 209 

leaves 193 

of  mountains 432 

protoplasm 186 

roots 183 

sap  (osmosis) 186 

seeds 205 

stems 188 

Plateau 392,409-415 

buttes 412, 413 

dissected 411 

mesas 412, 413 

old 413 

Poles  of  the  earth 3 

magnetic 35 

Pollen 201 

Pompeii  (pay'ee)      .....    444 


FIRST  YEAR  SCIENCE 


References  are  to  pages. 


Potash,  see  Soils. 

Potential  energy 45 

air  plants 209 

See  Energy. 

Prairies 402 

Prime  meridian 32 

Prism 127 

Properties  of  matter,  see  Matter. 
Proteins  (pro' tee-ins)    .   197,  235,  236 
Pro'toplasm 186,  198 

growth  in  the  body      ....    236 

in  bacteria 213 

Protozo'a    ...:....    218 
Pupil  of  the  eye 230 

sketch 231 

Radiation  of  heat 55 

Rainbow 128 

Rainfall 313-325 

and  caves 319 

and  lakes 322-325 

and  geysers 319 

forms  of,  snow,  hail,  etc.     .     .    156 

in  artesian  wells 318 

in  springs,  hot  and  cold  .       315-317 

map 155,  158 

measurement 154 

of  the  U.  S 157-160 

Rain  gauge 156 

Rapids 329-332 

Reflection  engine 63 

Reflection  of  light       .  58,  59,  62-64 

Refraction 60 

Respiration 225-227 

Ret'ina 230 

sketch 231 

Revolution  of  the  earth     .    .      26 
See  also  Earth. 

Rivers 332-361 

deltas 350 

development 342 

effects  upon  history     ....    353 

of  the  U.  S 354-360 

old 340 

young 332 

Rocks,  composition  of       ...      76 

kinds 77 

igneous 77 

metamor'phic 79 

sedimentary    .    .    .    .    .     77, 78 


Rocks  —  Continued 


structure 79 

subsoil 87 

varieties  of  stone 78 

weathering 82 

Roemer,  Ole,  Danish  astrono- 
mer (1644-1710),  on  light      .  64 

Rotation  of  the  earth     ...  22 
See  also  Earth. 

Sand  spits 297,  307 

picture 298 

Sandstone 78 

See  Soils. 

Sap 186 

Sap'rophytes 209 

Sargas'so  Sea     ......    282 

Satellites 11 

Saturn 4, 5 

picture 4 

satellites 11 

Sal'ivary  glands 233 

Salt  lakes 325 

Sand,  see  Soils. 

Sand  bars 297,  302 

Sand  dunes 302,387 

Sand  reefs 303,  307 

Sea,  the         68-71 

currents 281 

depths 275 

divisions 272 

floor 275 

islands 288 

life 248-251,269 

map  of  oceans 68 

shelf 273 

size 272 

temperature 279 

tides 284 

water 273 

waves 277 

See  also  Coasts,  Beaches. 

Seal 251 

Seasons,  change  of  ....     26-28 

Seaweed 248,  249 

of  the  Sargasso  Sea     ....    282 

picture 248 

Sedimentary  rocks    ....      77 
See  Rocks. 


INDEX 


References  are  to  pages. 


Seeds 202-205 

dispersal 205 

germination 206 

Senses,  the  five 230-232 

Sextant 456 

Shales 68 

See  Soils. 

Sidereal  day  (si-de're-al)      .    .  29 

Silt 95 

See  Soils. 

Sink-hole 319 

picture 317 

Skeleton 224 

Sleeping  sickness 218 

Sleet 157 

Snow 156,  363 

See  Glaciers. 

Soils 85-108 

agricultural 93 

alkali 103 

dry  farming 101 

fertile 90 

irrigation 102 

loam 88 

local 86 

mulches 101 

silt 95 

soil  water 96 

subsoil 87 

transported 86 

values 106 

Solar  day 28 

Solar  system 1-15 

ancient  ideas  of .  3,  22 

diagram 6 

nebular  hypothesis      ....  6 

Sol'stlce,  summer  and  winter    .  27 

Sound 65 

Specific      gravity     of      salt 

water 274 

Specific  heat 56,  57 

Spectrum 127 

Spinal  cord 225 

Springs,  hot  and  cold  ....  315 

sketch 314 

Stalac'tites 319 

Stalag'mites 319 

Sta'mens 201 

Standard  time 30 

map 31 


Starch 196 

Stars,  the 1-3 

distance 5 

Stigma  of  a  flower     ....    201 

Stomach 234 

Sto'mata 200 

Storms 167 

maps 172,  173 

sudden  changes 171 

weather  bureau 174 

Stratified  rock 79 

picture 80 

Striae  (stri'ee) 368 

Style  of  a  flower 201 

Suess,  Eduard,  Austrian  geol- 
ogist (1831 ) 70 

Sugar  as  food 235 

Summer 24,  25 

Sun 1-6 

center  of  solar  system  .  .  .  5,  6 
effect  upon  the  stars  .  .  .  .  2,  3 

energy  of 45 

in  plants 209 

revolution  of  earth  around  .  23-30 
rising  and  setting  .  .  .  .  22,  23 
size  and  distance  .  .  11,  12,  24,  25 

Sun  dial 28 

picture 29 

Swamps 325,  329 


Telegraph  .     .     .     .    .     .     .     39,  65 

apparatus 165,  166 

invention 166 

wireless 167 

Telephone 39,  167 

Temperate  zones  ....     '25-28 
Temperature,  average,  see  Cli- 
mate     279 

graphs 135 

maps 136,  137 

measurement 49-51 

of  land  and  water 137 

of  the  atmosphere 130 

of  the  ocean  waters     ....    187 

variations  of 131 

Terminal  moraine 367 

picture 369 

Terrestrial  winds 149 

Texas  fever     ,  .    220 


10 


FRST   YEAR   SCIENCE 


References  are  to  pages. 


Thermometers 49 

Fahrenheit  and  Centigrade       .      51 

Thunder-storms 163 

Tides 284 

flood  and  ebb 284 

in  Bay  of  Fundy 285 

spring  and  neap 287 

Tidewater 400 

Timber  line 256 

Time,  measurement  of  .     .    23,  28,  29 

standard 30-32 

Toadstools       211 

Tobacco       237 

Tornadoes       167 

pictures 168,  169 

Torrid  zone 25-28 

Tox'ins 216 

Trade  winds 149 

maps  of 149,  150,  151 

Transference  of  heat,  see  Heat. 
Transformation  of  heat,  see 
Heat. 

Tropics 27 

map 25 

Tse'tse  fly 218 

Typhoid  fever 216 


Universe,  ancient  ideas  of 
medieval  sketch  of      .     . 


3,22 
22 


Valleys  (see  Rivers)      .    .      332-361 

hanging 378 

picture   378,  379 

V-shaped 377 

Veins 228 

Ventilation 117 

Ven'tricle 229 

Venus 4,  5 

Vertebrates 224-235 

Vesta       6 

Vesu'vius 443 

Vit'reous  humor 231 

Volcanic  cones       451 

Volcanic  necks      .....  448 

Volcanoes       440 

decapitated  (caldera)       .     .     .  450 

distribution  of 452 

Mount  Lassen 442 

of  Hawaii 449 

of  the  Aleutian  Islands    .     ,     .  448 


Volcanoes  —  Continued 

of  the  Azores  \ 446 

of  the  U.  S 447 

Pelee .445 

Vesuvius 443 

Water,  characteristics  ....      71 

coasts 69 

obtained  by  evaporation       .     .     289 

of  the  globe 68 

of  the  sea 273 

properties        73 

soil  water        96 

specific  heat 56,  57 

temperature 139 

work  of  (erosion) 325 

See  Moisture,  Rainfall,  the  Sea. 

Waterspouts 168 

picture 171 

Waves  of  the  sea  .     .     .       277-279 

effect  upon  coasts    .     .     .       294-301 

Weather,  changes  in     .     .       171-174 

maps 136 

Weather  bureau 174 

Weathering 82 

See  Soils. 

Weight " .      10 

Whale 249 

Winds 142 

anemometer 144 

causes 143 

dust 386 

effects  of  earth's  rotation  upon    146 

•kinds 144,  145 

maps 149,  150,  151 

of  the  earth 149-154 

seasonal,  monsoons,  etc. .       152-154 

velocity 144 

wind-belts,  planetary       .     .     .    148 
work 

burying 387 

erosion 387 

Winter 24 

Worms    .  ...    220 


Year,  length  of     .     . 
Yeast 


Zones 


.      23 
.    211 

25-28 


SCIENCE 


First  Principles  of  Physics 

By  Professor  HENRY  S.  CARHART,  of  the  University  of  Michigan,  and 
H.  N.  CHUTE,  of  the  Ann  Arbor  High  School,  izmo,  cloth,  422  pages. 
Price,  $1.25. 

THE  present  volume  is  more  than  a  revision  of  the  authors' 
popular  High  School  Physics.  It  is  a  new  book  from  cover 
to  cover.  No  pains  have  been  spared  to  make  it  mechanically 
the  attractive  volume  which  the  increasing  interest  in  the  applica- 
tions of  this  practical  subject  deserves.  The  cuts  number  457 
and  will  be  found  to  constitute  a  prominent  feature  of  the  book. 
Especial  attention  has  been  given  to  the  language,  which  has 
been  made  unusually  simple  and  direct.  The  problems  are  nu- 
merous and  interesting,  and  in  them  the  difficulty  of  the  actual 
arithmetical  performance  is  reduced  to  a  minimum,  since  it  is 
recognized  that  the  purpose  of  problems  is  the  concrete  illustra- 
tion of  principles  rather  than  practice  in  arithmetic. 

Although  in  keeping  abreast  of  the  times  the  authors  have  in- 
troduced many  new  features,  they  have  been  careful  to  retain  the 
general  scheme  of  presentation,  and  the  just  proportions,  which 
made  their  former  books  so  popular.  The  space  given  to  the 
various  topics  is  such  as  logical  presentation  demands.  No  topic 
is  unduly  emphasized  in  an  effort  at  novelty  of  presentation.  Each 
subject  is  treated  concisely  and  is  divided  into  numerous  brief 
paragraphs  with  sub-headings,  in  order  to  aid  the  pupil  in  con- 
centrating his  mind  on  the  points  of  fundamental  importance. 

It  has  been  felt  that  many  recent  text-books  in  physics  have 
sacrificed  scientific  and  logical  presentation  in  the  effort  to  inter- 
est pupils  by  over-emphasis  of  some  aspect  of  the  science  which 
has  been  considered  attractive.  The  result  of  the  use  of  such 
books  has  been  a  one-sided  preparation  and  a  consequent  failure 
to  meet  college  requirements.  The  authors  of  First  Principles  of 
Physics  have  shown  that  it  is  possible  to  produce  a  book  which 
is  as  successful  as  their  former  texts  in  preparing  pupils  for  col- 
lege and  at  the  same  time  yields  to  no  competing  text-book  of 
physics  in  attractiveness. 


SCIENCE 

A  Laboratory  Guide  to  accompany  Carhart  and  Chute's 
First  Principles  of  Physics 

By  H.  N.  CHUTE,  of  the  High  School,  Ann  Arbor,  Michigan,    izmo, 
flexible  cloth,  124  pages.     Price,  50  cents. 

IN   this   Manual  the  author  has  chosen  such  problems  as  his 
experience  has  shown  to  be  within  the  range  of  the  beginner's 
skill. 

There  are  seventy  experiments  :  (i)  those  interesting  boys  and 
girls  alike  in  the  study  of  physics,  (2)  those  requiring  apparatus 
so  simple  as  to  be  easily  provided,  and  (3)  those  illustrating 
the  methods  of  modern  physics.  Special  attention  is  devoted  to 
the  preparation  of  the  note-book,  and  for  this  purpose  an  unusual 
array  of  excellent  illustrations  is  given  in  the  text. 

Laboratory  Exercises  in  Physics 

By  ROBERT  W.  FULLER  and  RAYMOND  B.  BROWNLEE,  Stuyvesant 
High  School,  New  York  City,     ismo,  cloth,  324  pages.  Price,  75  cents. 

THIS  Laboratory  Manual  is  intended  primarily  to  accompany 
Carhart  and  Chute's  First  Principles  of  Physics,  which  it 
follows  in   the  order  of  subjects.      It  is  so  arranged,  however, 
that  it  can  be  used  with  any  modern  text-book  in  Physics. 

There  are  ninety  experiments  in  the  book.  These  cover  a 
field  so  wide  that  from  them  may  be  selected  a  thorough  course 
which  can  be  given  with  the  apparatus  found  in  any  school.  At 
the  same  time  the  book  affords  enough  material  to  satisfy  teachers 
who  have  the  best-equipped  laboratories  at  their  disposal. 

While  the  experiments  meet  the  requirements  of  the  College 
Entrance  Board,  particular  effort  has  been  made  to  adapt  the 
work  to  the  needs  of  pupils  not  preparing  for  college. 

The  directions  are  simple  and  clear,  and  adapted  to  the  ability 
of  beginners  in  Physics.  There  are  full  instructions  on  the  mak- 
ing of  note-books. 

63 


SCIENCE 


First  Principles  of  Chemistry 

By  RAYMOND  B.  BROWNLEE,  Stuyvesant  High  School ;  ROBERT 
W.  FULLER,  Stuyvesant  High  School ;  WILLIAM  J.  HANCOCK,  Eras- 
mus Hall  High  School;  MICHAEL  D.  SOHON,  Morris  High  School; 
and  JESSE  E.  WHITSIT,  DeWitt  Clinton  High  School;  all  of  New 
York  City.  I2mo,  cloth,  425  pages.  Price,  $1.25. 

THIS  book  was  prepared  by  the  committee  or  teachers  that 
was  called  upon  to  frame  the  syllabus  in  Chemistry  for  New 
York  State.     Its  three  fundamental  features  are  :  — 

1.  The  experimental  evidence  precedes  the  chemical  theory. 

2.  The  historical  order  is  followed  as  far  as  possible  in  de- 
veloping the  theory. 

3.  The  practical  aspects  of  the  science  are  emphasized. 

In  selecting  their  material  the  authors  have  been  governed 
wholly  by  what  they  consider  its  intrinsic  value  to  the  elementary 
student,  without  reference  to  its  traditional  place  in  a  text-book. 

To  give  the  pupil  some  idea  of  the  great  commercial  impor- 
tance of  chemistry  a  number  of  typical  manufacturing  processes 
have  been  described  and  illustrated.  When  a  substance  is  manu- 
factured in  several  ways  the  authors  have  given  the  process  most 
extensively  used  in  this  country.  The  commercial  production  of 
copper,  aluminum,  iron,  and  carborundum  has  been  described 
somewhat  in  detail,  as  these  are  notable  examples  of  modern 
chemical  processes. 

An  important  feature  is  the  brief  summary  and  the  test  exer- 
cises given  at  the  end  of  each  chapter. 

Laboratory  Exercises  to  Accompany  First  Principles 

of   Chemistry 

By  the  authors  of  the  First  Principles  of  Chemistry.  I2mo,  flexible 
cloth,  147  pages.  Price,  50  cents. 

IN  this  manual  are  included  seventy-one  experiments,  divided 
into  three  groups.     Group  A  consists  of  forty-four  experiments 
which  all  students  should  perform.    Group  B  contains  quantitative 
experiments,  and  Group  C  includes  several  extremely  interesting 
experiments  dealing  with  the  practical  applications  of  Chemistry. 

64 


SCIENCE 


Household  Chemistry  for  Girls 

By  J.  MAuf)  BLANCHARD,  High  School,  Los  Angeles,  California 
lamo,  cloth,  108  pages.  Price,  50  cents. 

THE  author's  purpose  is  to  outline  a  strong  course  in  chemis- 
try, especially  suited  to  girls  of  high  school  age.  Though 
the  ultimate  aim  is  the  training  of  intelligent  homemakers,  it  is  a 
manual  of  chemistry,  not  of  domestic  science.  It  is  therefore 
suitable  for  a  purely  academic  high  school,  no  less  than  for  a 
polytechnic  high  school,  where  a  rigorous  course  in  household 
chemistry  forms  a  necessary  foundation  for  the  work  in  domestic 
science.  The  choice  of  subjects  is  based  in  a  general  way  on  the 
following  scheme :  — 

What  we  breathe. 

What  we  drink  and  use  for  cleaning. 

What  we  use  for  fuels  and  illuminants. 

Chemical  nature  of  common  substances. 

Foods  and  food  values. 

Adulterants  and  simple  methods  for  their  detection. 

Textiles  —  care  of  textiles,  removal  of  stains,  etc. 
The  second  half  of  the  book,  beginning  with  Experiment  28,  is 
devoted  to  qualitative  experiments  in  organic  chemistry,  as  delicate 
quantitative  experimentation  is  beyond  the  ability  of  high  school 
pupils.  Supplementary  reading  is  of  course  advisable  in  this  con- 
nection ;  with  this  in  view,  a  full  list  of  library  text-books  is  given, 
and  definite  references  to  these  accompany  the  experiments. 

High  School  Physics 

By  Professor  HENRY  S.  CARHART,  of  the  University  of  Michigan,  and 
H.  N.  CHUTE,  of  the  Ann  Arbor  High  School.  New  Edition,  thor- 
oughly revised.  I2mo.  cloth,  ^/|/|  pages.  Price,  $1.25. 

THE  task  of  arousing  interest,  and  of  emphasizing  especially 
attractive  aspects  of  the  science,  is  looked  upon  as  the  prov- 
ince of  the  individual  teacher.     This  text-book  aims  simply  at  a 
clear-cut   statement   of  general  principles,   giving  each   weight 
according  to  the  scientific  importance  which  it  possesses. 

65 


SCIENCE 

Text-Book  of  Cooking  for  Secondary  Schools 

By  CARLOTTA  C.  GREEK,  East  Technical  High  School,  Cleveland. 
I2mo,  cloth,  coo  pages.    Price,  oo  cents. 

THIS  is  not  a. book  of  recipes  —  it  is  literally  a  text-book  of 
cooking,  in  which  the  practice  of  cooking  is  developed  in  a 
logical  manner.  The  methods  of  cooking  are  practical,  and  the 
author  shows  the  scientific  principles  on  which  they  are  based. 
Statements  thus  involving  applied  science  are  carefully  kept 
within  the  understanding  of  pupils  in  the  secondary  school. 

The  text-book  is  divided  into  two  parts.  Part  I  treats  of  The 
Cooking  of  Foods,  Part  II  of  Table  Service  and  Food  Values  of 
Foods.  Together  the  two  parts  furnish  material  for  one  year's 
work  of  four  or  five  lessons  a  week,  or  for  two  years'  work  if  the 
curriculum  provides  but  two  lessons  a  week. 

Part  I  is  a  guide  to  teach  pupils  to  cook.  The  pupils  follow 
established  recipes  and  are  taught  to  consider  the  processes  of 
cooking  as  experiments  in  scientific  study.  Added  to  recipes 
and  directions  are  suggestions  to  aid  the  pupil  to  appreciate  the 
significance  of  each  step  and  to  understand  the  change  that  is 
taking  place  in  the  substances  he  is  using.  In  the  reviews  the 
pupil  is  helped  to  work  out  his  own  scheme  for  preparing  a  meal. 

Part  II  adds  to  the  planning  and  cooking  of  meals  a  practical 
method  of  calculating  food  values.  Special  attention  is  given  to 
cooking  and  serving  without  a  maid. 

The  book  is  richly  illustrated. 

The  entire  book  has  been  worked  out  and  tested  in  the  class- 
room of  one  of  the  largest  vocational  schools  in  America. 

Descriptive  Inorganic  General  Chemistry 

A  text-book  for  colleges,  by  the  late  Professor  PAUL  C.  FREER.    Revised 
edition.    8vo,  cloth,  559  pages.    Price,  $3.00. 

THIS  is  a  text-book  in  General  Chemistry  for  colleges  and  uni- 
versities.    It  aims  to  give  a  systematic  course  of  chemistry 
by  stating  certain  initial  principles,  and  connecting  logically  all 
the  resultant  phenomena. 

66 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
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OVERDUE. 


-a  6  i 


AUU   6  1939 


LD  21-100m-8,'34 


YC  22542 


l\ 


UNIVERSITY  OF  CAUFORNIA  LIBRARY 


